urinalysis case study quizlet

VICTORIA J. SHARP, MD, DANIEL K. LEE, MD, AND ERIC J. ASKELAND, MD

A more recent article on  office-based urinalysis  is available.

Am Fam Physician. 2014;90(8):542-547

Author disclosure: No relevant financial affiliations.

Urinalysis is useful in diagnosing systemic and genitourinary conditions. In patients with suspected microscopic hematuria, urine dipstick testing may suggest the presence of blood, but results should be confirmed with a microscopic examination. In the absence of obvious causes, the evaluation of microscopic hematuria should include renal function testing, urinary tract imaging, and cystoscopy. In a patient with a ureteral stent, urinalysis alone cannot establish the diagnosis of urinary tract infection. Plain radiography of the kidneys, ureters, and bladder can identify a stent and is preferred over computed tomography. Asymptomatic bacteriuria is the isolation of bacteria in an appropriately collected urine specimen obtained from a person without symptoms of a urinary tract infection. Treatment of asymptomatic bacteriuria is not recommended in nonpregnant adults, including those with prolonged urinary catheter use.

Urinalysis with microscopy has proven to be an invaluable tool for the clinician. Urine dipstick testing and microscopy are useful for the diagnosis of several genitourinary and systemic conditions. 1 , 2 In 2005, a comprehensive review of urinalysis was published in this journal. 3 This article presents a series of case scenarios that illustrate how primary care physicians can utilize the urinalysis in common clinical situations.

Microscopic Hematuria: Case 1

Microscopic hematuria is common and has a broad differential diagnosis, ranging from completely benign causes to potentially invasive malignancy. Causes of hematuria can be classified as glomerular, renal, or urologic 3 – 5 ( Table 1 6 ) . The prevalence of asymptomatic microscopic hematuria varies among populations from 0.18% to 16.1%. 4 The American Urological Association (AUA) defines asymptomatic microscopic hematuria as three or more red blood cells per high-power field in a properly collected specimen in the absence of obvious causes such as infection, menstruation, vigorous exercise, medical renal disease, viral illness, trauma, or a recent urologic procedure. 5 Microscopic confirmation of a positive dipstick test for microscopic hematuria is required. 5 , 7

DIAGNOSTIC APPROACH

Case 1: microscopic hematuria.

A 58-year-old truck driver with a 30-year history of smoking one pack of cigarettes per day presents for a physical examination. He reports increased frequency of urination and nocturia, but does not have gross hematuria. Physical examination reveals an enlarged prostate. Results of his urinalysis with microscopy are shown in Table 2 .

Based on this patient's history, symptoms, and urinalysis findings, which one of the following is the most appropriate next step?

A. Repeat urinalysis in six months.

B. Obtain blood urea nitrogen and creatinine levels, perform computed tomographic urography, and refer for cystoscopy.

C. Treat with an antibiotic and repeat the urinalysis with microscopy.

D. Inform him that his enlarged prostate is causing microscopic hematuria, and that he can follow up as needed.

E. Perform urine cytology to evaluate for bladder cancer.

The correct answer is B .

For the patient in case 1 , because of his age, clinical history, and lack of other clear causes, the most appropriate course of action is to obtain blood urea nitrogen and creatinine levels, perform computed tomographic urography, and refer the patient for cystoscopy. 5 An algorithm for diagnosis, evaluation, and follow-up of patients with asymptomatic microscopic hematuria is presented in Figure 1 . 5 The AUA does not recommend repeating urinalysis with microscopy before the workup, especially in patients who smoke, because tobacco use is a risk factor for urothelial cancer ( Table 3 ) . 5

A previous article in American Family Physician reviewed the American College of Radiology's Appropriateness Criteria for radiologic evaluation of microscopic hematuria. 8 Computed tomographic urography is the preferred imaging modality for the evaluation of patients with asymptomatic microscopic hematuria. 5 , 8 It has three phases that can detect various causes of hematuria. The non–contrast-enhanced phase is optimal for detecting stones in the urinary tract; the nephrographic phase is useful for detecting renal masses, such as renal cell carcinoma; and the delayed phase outlines the collecting system of the urinary tract and can help detect urothelial malignancies of the upper urinary tract. 9 Although the delayed phase can detect some bladder masses, it should not replace cystoscopy in the evaluation for bladder malignancy. 9 After a negative microscopic hematuria workup, the patient should continue to be followed with yearly urinalysis until at least two consecutive normal results are obtained. 5

In patients with microscopic hematuria, repeating urinalysis in six months or treating empirically with antibiotics could delay treatment of potentially curable diseases. It is unwise to assume that benign prostatic hyperplasia is the explanation for hematuria, particularly because patients with this condition typically have risk factors for malignancy. Although urine cytology is typically part of the urologic workup, it should be performed at the time of cystoscopy; the AUA does not recommend urine cytology as the initial test. 5

Dysuria and Flank Pain After Lithotripsy: Case 2

After ureteroscopy with lithotripsy, a ureteral stent is often placed to maintain adequate urinary drainage. 10 The stent has one coil that lies in the bladder and another that lies in the renal pelvis. Patients with ureteral stents may experience urinary frequency, urgency, dysuria, flank pain, and hematuria. 10 They may have dull flank pain that becomes sharp with voiding. This phenomenon occurs because the ureteral stent bypasses the normal nonrefluxing uretero-vesical junction, resulting in transmission of pressure to the renal pelvis with voiding. Approximately 80% of patients with a ureteral stent experience stent-related pain that affects their daily activities. 11

POTENTIALLY MISLEADING URINALYSIS

Case 2: dysuria and flank pain after lithotripsy.

A 33-year-old woman with a history of nephrolithiasis presents with a four-week history of urinary frequency, urgency, urge incontinence, and dysuria. She recently had ureteroscopy with lithotripsy of a 9-mm obstructing left ureteral stone; she does not know if a ureteral stent was placed. She has constant dull left flank pain that becomes sharp with voiding. Results of her urinalysis with microscopy are shown in Table 4 .

A. Treat with three days of ciprofloxacin (Cipro), and tailor further antibiotic therapy according to culture results.

B. Treat with 14 days of ciprofloxacin, and tailor further antibiotic therapy according to culture results.

C. Obtain a urine culture and perform plain radiography of the kidneys, ureters, and bladder.

D. Perform a 24-hour urine collection for a metabolic stone workup.

E. Perform computed tomography.

The correct answer is C .

The presence of a ureteral stent causes mucosal irritation and inflammation; thus, findings of leukocyte esterase with white and red blood cells are not diagnostic for urinary tract infection, and a urine culture is required. In this setting, plain radiography of the kidneys, ureters, and bladder would be useful to determine the presence of a stent. If a primary care physician identifies a neglected ureteral stent, prompt urologic referral is indicated for removal. Retained ureteral stents may become encrusted, and resultant stone formation may lead to obstruction. 10

Flank discomfort and recent history of urinary tract manipulation suggest that this is not an uncomplicated urinary tract infection; therefore, a three-day course of antibiotics is inadequate. Although flank pain and urinalysis suggest possible pyelonephritis, this patient should not be treated for simple pyelonephritis in the absence of radiography to identify a stent. A metabolic stone workup may be useful for prevention of future kidney stones, but it is not indicated in the acute setting. Finally, although computed tomography would detect a ureteral stent, it is not preferred over radiography because it exposes the patient to unnecessary radiation. Typically, microscopic hematuria requires follow-up to ensure that there is not an underlying treatable etiology. In this case , the patient's recent ureteroscopy with lithotripsy is likely the etiology.

Urinalysis in a Patient Performing Clean Intermittent Catheterization: Case 3

Case 3: urinalysis in a patient performing clean intermittent catheterization.

A 49-year-old man who has a history of neurogenic bladder due to a spinal cord injury and who performs clean intermittent catheterization visits your clinic for evaluation. He reports that he often has strong-smelling urine, but has no dysuria, urge incontinence, fever, or suprapubic pain. Results of his urinalysis with microscopy are shown in Table 5 .

A. Inform the patient that he has a urinary tract infection, obtain a urine culture, and treat with antibiotics.

B. Refer him to a urologist for evaluation of a complicated urinary tract infection.

C. Perform computed tomography of the abdomen and pelvis to evaluate for kidney or bladder stones.

D. Inform him that no treatment is needed.

E. Obtain a serum creatinine level to evaluate for chronic kidney disease.

The correct answer is D .

Although the urinalysis results are consistent with a urinary tract infection, the clinical history suggests asymptomatic bacteriuria. Asymptomatic bacteriuria is the isolation of bacteria in an appropriately collected urine specimen obtained from a person without symptoms of a urinary tract infection. 12 The presence of bacteria in the urine after prolonged catheterization has been well described; one study of 605 consecutive weekly urine specimens from 20 chronically catheterized patients found that 98% contained high concentrations of bacteria, and 77% were polymicrobial. 13

Similar results have been reported in patients who perform clean intermittent catheterization; another study of 1,413 urine cultures obtained from 407 patients undergoing clean intermittent catheterization found that 50.6% contained bacteria. 14 Guidelines from the Infectious Diseases Society of America recommend against treatment of asymptomatic bacteriuria in nonpregnant patients with spinal cord injury who are undergoing clean intermittent catheterization or in those using a chronic indwelling catheter. 12

In the absence of symptoms of a urinary tract infection or nephrolithiasis, there is no need to culture the urine, treat with antibiotics, refer to a urologist, or perform imaging of the abdomen and pelvis. There is no reason to suspect acute kidney injury in this setting; thus, measurement of the serum creatinine level is also unnecessary.

Data Sources : Literature searches were performed in PubMed using the terms urinalysis review, urinalysis interpretation, microscopic hematuria, CT urogram, urinary crystals, indwelling ureteral stent, asymptomatic bacteriuria, and bacteriuria with catheterization. Guidelines from the American Urological Association were also reviewed. Search dates: October 2012 and June 2013.

Wu X. Urinalysis: a review of methods and procedures. Crit Care Nurs Clin North Am. 2010;22(1):121-128.

Hardy PE. Urinalysis interpretation. Neonatal Netw. 2010;29(1):45-49.

Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review [published correction appears in Am Fam Physician . 2006;74(7):1096]. Am Fam Physician. 2005;71(6):1153-1162.

Cohen RA, Brown RS. Clinical practice. Microscopic hematuria. N Engl J Med. 2003;348(23):2330-2338.

American Urological Association. Diagnosis, evaluation and follow-up of asymptomatic microhematuria (AMH) in adults. http://www.auanet.org/education/asymptomatic-microhematuria.cfm . Accessed June 6, 2014.

Ahmed Z, Lee J. Asymptomatic urinary abnormalities. Hematuria and proteinuria. Med Clin North Am. 1997;81(3):641-652.

Rao PK, Jones JS. How to evaluate ‘dipstick hematuria’: what to do before you refer. Cleve Clin J Med. 2008;75(3):227-233.

Choyke PL. Radiologic evaluation of hematuria: guidelines from the American College of Radiology's Appropriateness Criteria. Am Fam Physician. 2008;78(3):347-352.

Sadow CA, Wheeler SC, Kim J, Ohno-Machado L, Silverman SG. Positive predictive value of CT urography in the evaluation of upper tract urothelial cancer. AJR Am J Roentgenol. 2010;195(5):W337-W343.

Haleblian G, Kijvikai K, de la Rosette J, Preminger G. Ureteral stenting and urinary stone management: a systematic review. J Urol. 2008;179(2):424-430.

Joshi HB, Stainthorpe A, MacDonagh RP, Keeley FX, Timoney AG, Barry MJ. Indwelling ureteral stents: evaluation of symptoms, quality of life and utility. J Urol. 2003;169(3):1065-1069.

Nicolle LE, Bradley S, Colgan R, Rice JC, Schaeffer A, Hooton TM Infectious Diseases Society of America; American Society of Nephrology; American Geriatric Society. Infectious Diseases Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults [published correction appears in Clin Infect Dis . 2005;40(10):1556]. Clin Infect Dis. 2005;40(5):643-654.

Warren JW, Tenney JH, Hoopes JM, Muncie HL, Anthony WC. A prospective microbiologic study of bacteriuria in patients with chronic indwelling urethral catheters. J Infect Dis. 1982;146(6):719-723.

Bakke A, Digranes A. Bacteriuria in patients treated with clean intermittent catheterization. Scand J Infect Dis. 1991;23(5):577-582.

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• URINALYSIS CASES AND CRITICAL THINKING

Gerald D. Redwine, PhD, MT(ASCP)

The physical and chemical examination of urine samples plays an essential role in the diagnosis of patients’ pathological conditions. However, the sheer number of routine urinalysis can minimize their significance, especially considering that most analyses are automated, which can foster complacency for less than apparent problems. As a result of seemingly more critical concerns, one may defer the interpretation for the clinician to assess. Nevertheless, detecting abnormal results and possible causes is required, regardless of whether the analysis was manual or automated. Knowing the effects of pigmentation, drugs, pH, and ascorbic acid, for example, are samples that always need attention.

Manual analysis is further complicated, with several idiosyncrasies innate to manufacturers. For example, differences in popular brands, such as, Multistix, that requires reading each chemical pad at the specific time indicated. But the Chemstrip and vChem strips readings are stable between one and two minutes, except leukocytes read at two minutes, all necessitating the need for special attention to the manufacturers’ instructions. Concerning ascorbic acid, knowing that Chemstrip eliminates ascorbic acid interference with blood by overlaying the pad with iodate, and the vChem strips have a detection pad for the substance; in contrast, knowing that the Multistix has neither, is essential. Finally, knowing to ignore the different coloration on the perimeter of the pad on all strips and asking for a recollect on extremely high pH is also vital.

How are the critical thinking skills needed for a urinalysis assessment best developed? In academia, it seemed best, following initial training, to have students complete weeks of daily intensive practice of the entire urinalysis (physical, chemical, and microscopic) in an open lab setting on multiple patient samples. In combination with these analyses, they were given case studies like the ones administered later in a practical examination. The following is a composite of the answer stating what they thought was the most probable cause to three of the 17 cases given on their exam, using Multistix, with further comments in parenthesis. Assessments constrained the students to answer the question under the given condition, knowing they would ask for a recollect in some instances.

• What would explain the apparent disagreement between the nitrite and leukocyte reaction?
• What accounts for the clarity of the sample in the chemical examination?
• What does the Acetest suggest about the chemical reactions, based on literature?
• Non-nitrate reducing organism. (i.e., bacteria, yeast, trichomonads, and chlamydia) Or Trauma. (Other less likely possibilities.)
• Large blood. (Also slightly enhanced the protein.)
• More sensitive because of the added glycine. (Glycine detects acetone. vChem strips have the same.)
• What could explain the single most unexpected finding within the chemical reactions?
• What could account for the protein and SSA discrepancy?
• What should the adjusted strip value read?
• What is the definitive source(s) for reporting the final specific gravity (SG) reading (manual/analyzer/and or name another source) on this specimen?
• With an SG = 1.040, what value is the final specific gravity?
• Negative leukocytes could result from any or all three of the following. 1) Alkalinity 2) >3g/dL glucose 3) High specific gravity.
• Alkaline pH can cause a false positive protein; also, the blood that is missing in the supernatant for the SSA could account for the 2+ SSA.
• Because pH is ≥ 6.5, then add .005 to the dip strip value. Strip SG = 1.035 . (Multistix only)
• Because of the ≥ 100 protein, then run on the refractometer. (Total Solid (TS) meter/Refractometer.)
• Subtract 0.003 for every 1 g/dl protein; subtract 0.004 for every 1 g/dl glucose. Report SG: 1.026 .
• What could explain the disagreement that exists within the chemical reactions?
• Explain the correlation between chemical reactions and the SSA?
• What are the two specific adjustments needed for the specific gravity?
• What is the final strip specific gravity?
• A non-nitrite reducing microbe such as Trichomonas or Chlamydia . Or postrenal trauma. (Other nitrite negative possibilities. Also, if not for the trace protein, ascorbic acid is suspect.) Best observation: Yellow-Green ~ Biliverdin. False-negative bilirubin. Hence, the need for a recollection and run on a fresh sample to ascertain the true values.
• Expected the SSA to be greater. Alkaline pH can cause a false positive protein, or in this case, falsely increase the value.
• Because pH is ≥ 6.5, then add .005 to the dip strip value. Because of the ≥ 100 protein, then run on the refractometer. TS (Total Solid) meter/Refractometer. (Multistix only)
• Strip SG = 1.015.

Responses to the open lab concept, despite significantly more than usual time commitment on behalf of all involved, and reagents, the sacrifices were met with positive feedback from the students on superseding their learning outcomes. The learning outcomes summarized is critical thinking applied to urinalysis case studies.

Reference: Brunzel, N. A., MS, MLS(ASCP) CM . Fundamentals of Urine and Body Fluid Analysis , 4th Edition

Gerald D. Redwine is an associate professor at Texas State University Clinical Laboratory Science Program in San Marcos, Texas.

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Urinalysis Quiz

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Educational Case: Acute Cystitis

Ryan l. frazier.

1 Department of Pathology, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA. Huppmann is now at the University of South Carolina School of Medicine Greenville, Greenville, SC, USA.

Alison R. Huppmann

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040 . 1

Primary Objective

Objective UTB2.1 : Acute Cystitis . Discuss the typical clinical symptomatology of acute cystitis and the organisms commonly causing this disorder.

Competency 2 Organ System Pathology; Topic UTB: Bladder; Learning Goal 2: Bladder Infection.

Secondary Objectives

Objective M2.11: Urine Studies for Cystitis . Explain the role of urine studies, including culture, in selecting antimicrobial therapy for infectious cystitis.

Competency 3 Diagnostic Medicine and Therapeutic Pathology; Topic M: Microbiology; Learning Goal 2: Antimicrobials.

Objective M2.12: Diagnosis of UTI . Describe a testing strategy for a typical uncomplicated community acquired urinary tract infection (UTI) versus a nosocomial UTI in a patient with a Foley catheter and list the key microbiological tests in diagnosis of UTIs.

Patient Presentation

A 27-year-old woman presents to her primary care physician with a report of urinating more frequently and pain with urination. She denies blood in her urine, fevers, chills, flank pain, and vaginal discharge. She reports having experienced similar symptoms a few years ago and that they went away after a course of antibiotics. The patient has no other past medical problems. Pertinent history reveals she has been sexually active with her boyfriend for the past 4 months and uses condoms for contraception. She reports 2 lifetime partners and no past pregnancies or sexually transmitted diseases. Her last menstrual period was 1 week ago.

Diagnostic Findings, Part 1

On physical exam, the patient is afebrile, normotensive, and non-tachycardic. She appears well on observation. She has a soft, nondistended abdomen with normoactive bowel sounds. On palpation, she has moderate discomfort in her suprapubic region but no costovertebral angle (CVA) tenderness. A pelvic exam is normal with no evidence of abnormal vaginal or cervical discharge or inflammation.

Questions/Discussion Points, Part 1

What is the differential diagnosis for this patient which diagnosis is most likely and why.

The top entities in the differential diagnosis include a UTI, vaginitis/cervicitis, and pyelonephritis. The most likely diagnosis in this patient is a UTI, specifically, acute cystitis. Classic UTI symptoms include urinary frequency and urgency and dysuria. Other complaints could include suprapubic pain or discomfort, hesitancy, nocturia, and even gross hematuria. Urinary tract infections are classified by the anatomical location in which the infection and inflammation occur. Risk factors that this patient possesses, which will be discussed later, are female sex, age, recent sexual activity, and a history of prior UTI, which we can infer from her report of previous similar symptoms. 2

Vaginitis and cervicitis should also be considered in this patient given her history of sexual activity. However, the patient has no reported vaginal discharge or signs of these infections on pelvic examination. Another important diagnosis to consider is pyelonephritis, which involves infection of the upper urinary tract. This is also not likely given her lack of fever, flank pain, and other key symptoms which will be discussed in a later section.

Is Laboratory Testing Required To Confirm the Diagnosis in This Patient?

Laboratory studies are not needed in this patient due to the high likelihood of a UTI, and empirical treatment can be administered. Thus, the importance of a good history and physical exam is highly emphasized when caring for a patient with a possible UTI. Uncomplicated UTIs are commonly observed and treated in the outpatient setting; they are increasingly being diagnosed without an in-person visit via telephone. 2

Which Populations Are at Higher Risk of Contracting a UTI? Why? Discuss the Terms “Uncomplicated UTI” Versus “Complicated UTI”

Urinary tract infections are due to the colonization of the urinary tract by microbes. Certain populations are at higher risk of infections of the urinary tract. Women are among those most affected by UTIs, with a lifetime incidence rate of almost 50%. 3 The difference between the sexes is attributed to women’s shorter urethral length. Women who are sexually active are also at risk of UTI due to the proximity of the urethral meatus to the flora-rich anus. If the patient is a premenopausal, otherwise healthy, and nongravid female, as in this case, she has developed an “uncomplicated” infection. 2 , 4

Patients who are predisposed to conditions that make colonization more likely or are exposed to microbes that are more facile in evading the body’s natural protective mechanisms are more apt to contract UTIs, and their infections can be more difficult to treat. These patients have “complicated” infections. Numerous conditions make a patient more susceptible to UTI. These include underlying medical problems or structural abnormalities of the urinary tract such as urinary obstruction, vesicoureteral reflux, underlying urinary tract disease, diabetes, renal papillary necrosis, immunosuppression (medically induced or as a result of HIV infection), treatment with antibiotics, pregnancy, menopause, and spinal cord injuries. 4 The elderly are also at increased risk of UTI, particularly men, many of whom develop obstructive uropathy from benign prostatic hypertrophy. 2 , 4

When Should a Diagnosis of Pyelonephritis Be Suspected?

Infection of the kidney is termed pyelonephritis. These patients tend to present acutely with “upper tract signs,” to include fever, chills, flank pain, and CVA tenderness. Symptoms of lower UTI can also be present; however, this is not usually the case. The clinical presentation may vary and can be life-threatening. In the most severely ill, patients may present in septic shock, with hypotension, tachycardia, and tachypnea, especially when infected with a gram-negative organism. 4

Which Laboratory Studies Can Be Performed on Urine To Evaluate a Potential UTI? What Is the Diagnostic Value of Each Test?

Laboratory tools are commonly utilized in the investigation of UTIs for patients with a complicated UTI, recurrent infections, or an unclear diagnosis based purely on history and physical exam. Again, test results should always be correlated with clinical findings, as false-positive or false-negative results can occur through multiple avenues. Available tests include a urine dipstick, urinalysis with microscopy, and culture and gram stain with sensitivity testing. The first 2 of these have the potential to be performed in physicians’ offices. A clean-catch midstream specimen should be submitted to avoid contamination from vaginal or penile microorganisms. Patients should be given a 2% castile soap towelette and instructed in appropriate specimen collection. Men should cleanse the glans, retracting the foreskin first if uncircumcised. Women should cleanse the periurethral area after spreading the labia. Identification of lactobacilli and epithelial cells from the vagina suggest contamination. 4

General features of the urine can first be examined to include the color, clarity, and odor; but these features are nonspecific. For example, cloudy urine can be caused by the presence of white blood cells and/or bacteria in a UTI; but it can also be caused by numerous other pathologic and non-pathologic substances.

Urine dipstick studies, primarily searching for leukocyte esterase and nitrites, are useful when the pretest probability of UTI is high. Leukocyte esterase is an enzyme possessed by white blood cells. Thus, a positive urine dipstick for leukocyte esterase indicates the presence of inflammatory cells in the patient’s urinary tract. Inflammatory cells in the urine are not specific for a UTI, as leukocytes can also be present in other situations such as glomerulonephritis and vaginal contamination. Nitrite is a breakdown product of nitrates, which are normally found in a healthy patient’s urine. The dipstick test for nitrite is specific for gram-negative organisms which possess an enzyme enabling them to reduce nitrates. It follows, then, that this test is less useful in the setting of potential gram-positive microbe infection. Also notable is that the nitrite test can be falsely negative in a patient with abundant fluid intake and frequent urination. 2 Multiple other factors including medications, diet, and specimen handling can affect urine dipstick results, as can inappropriate handling or expiration of test strips.

Urinalysis with microscopy provides a window into the kidney and urinary tract. The presence of red blood cells, white blood cells, casts, crystals, and bacteria aid in many diagnoses. Specific to UTI, the presence of white blood cells and red blood cells indicates inflammation and, potentially, infection in the urinary tract. 2 Pyuria, the presence of leukocytes in the urine, is not specific to UTIs as noted above; but the absence of leukocytes should cause one to question a diagnosis of UTI unless the culture is positive. The identification of crystals might suggest the presence of renal calculi, which can serve as a nidus for infection. In fact, some stones (eg, struvite) are the direct result of infection with urea-splitting organisms. Overall, urinalysis is useful; however, the clinical history still plays a key role to avoid under- and overdiagnosis. 4

Urine culture is the gold standard diagnostic tool for diagnosing UTIs. 2 , 4 As stated previously, in patients with a convincing clinical history and physical exam consistent with uncomplicated cystitis, no culture is necessary. However, in patients with complicated, severe upper urinary tract, or recurrent UTIs, urine culture should not be foregone, as it is necessary for determining the causative organism and, consequently, for guiding appropriate therapeutic intervention. Furthermore, growth of the organism in culture facilitates sensitivity studies, in which pharmacologic agents are tested on the microbe isolated from the patient. This testing provides medical personnel with information regarding the efficacy of potential therapeutic options in the form of minimal inhibitory concentrations. This information guides narrowing of antibiotic choice from whichever broad-spectrum treatment was initiated when a UTI was first suspected. 2 Some organisms such as Ureaplasma urealyticum may not be grown on routine cultures, so a false-negative result is possible. False-positive results are rare, other than due to contamination, which should be suspected in most cases with growth of multiple types of bacteria or vaginal flora. 4

What Is Asymptomatic Bacteriuria?

The diagnosis of asymptomatic bacteriuria requires 2 criteria: (1) The urine is culture-positive and (2) the patient does not have symptoms or signs of a UTI. The level of bacteria in culture should reach ≥10 5 CFU/mL, although it can be lower in catheterized patients (≥10 2 CFU/mL). Asymptomatic bacteriuria is only treated in some groups of patients, including those who are pregnant or undergoing urologic procedures, as it otherwise does not correlate with symptomatic disease or complications. 2

Which Microorganisms Most Commonly Cause Acute Cystitis?

In general, gram-negative aerobic rods are the most commonly isolated pathogens implicated in UTIs. 2 Escherichia coli is the most common causative organism of UTIs, especially in sexually active young women. 2 , 4 Microorganisms such as uropathogenic E coli (UPEC) with an enhanced ability to bind and to adhere to urinary tract epithelia are more capable of causing infection. Adhesins and pili resistant to the innate immune mechanisms of defense are among the advantageous traits that particularly virulent strains of UPEC possess. 4

A variety of other Enterobacteriaceae (discussed below) are also found in the setting of catheter-associated UTIs (CAUTIs). However, gram-positive organisms are clinically significant in some settings. Staphylococcus saprophyticus is not infrequently implicated in uncomplicated UTIs in young, sexually active women. 2 Group B Streptococcus (GBS, Streptococcus agalactiae ) is of particular concern in pregnant patients. In 1 prospective study, GBS was the second most isolated pathogen behind E coli in the urine of asymptomatic bacteriuric pregnant women. 5 Screening pregnant women for asymptomatic bacteriuria plays an important role in decreasing the risk of pyelonephritis during pregnancy. 6 , 7 Table 1 summarizes the typical microorganisms identified in complicated and uncomplicated UTIs along with the appropriate laboratory testing.

Common Causative Organisms and Indicated Laboratory Tests for Patients With Uncomplicated and Complicated Urinary Tract Infections (UTIs).

Abbreviation: STI, sexually transmitted infection.

Discuss CAUTIs and Their Difference From Non-CAUTIs, Including Clinical Features and Causative Microorganisms

Per the Infectious Diseases Society of America, 8 both clinical and laboratory criteria should be met to make the diagnosis of a catheter-associated UTI (CAUTI). The patient should have signs or symptoms of a UTI and no other known source of infection. Culture of the patient’s urine sample should yield greater than 10 3 colony-forming units (CFU)/mL of at least 1 species of bacteria. The cultured urine should be from a single specimen in those patients who are still catheterized. Catheter-associated UTI can also be diagnosed in those whom have had a catheter removed within the preceding 48 hours, in which case a midstream voided urine is the appropriate specimen.

Catheter-associated UTIs are a type of complicated UTI and are among the most common nosocomial (hospital-acquired) infections in the United States. 4 Urinary catheters facilitate the ascent of microbes into the urinary tract. There are different methods of catheterization, for example, clean intermittent catheterization, indwelling urethral catheters, and suprapubic catheters. Microorganisms can be introduced during the procedure of catheterization despite the implementation of sterilization methods. Also, without appropriate catheter care, these indwelling devices can become a nidus for infection, permitting various other flora to travel along the tube and into the urinary tract. 4

As previously mentioned, E coli is the most common causative organism of acute cystitis in uncomplicated UTIs. 4 It is also the most commonly isolated organism in CAUTI. 8 , 9 However, patients with catheters are at higher risk of infection by organisms less commonly seen in non-catheterized patients. Patients who are catheterized for both short and long periods of time are at increased risk of infection with fungal organisms as well as Enterobacteriaceae such as Klebsiella , Serratia , Enterobacter , Pseudomonas , Enterococcus , and Proteus species. 4 , 6 , 9 These organisms are exceptionally well-adapted for invasion given the ability many of them possess to form biofilms. The longer a patient is catheterized, the more likely they are to develop bacteriuria, a symptomatic infection, and potentially colonization of the urinary tract. 4 Thus, timely removal of catheters when no longer necessary is wise.

How Should Patients With UTIs Be Treated?

The choice of therapy for UTIs depends on the clinical treatment setting, and whether it is a complicated or uncomplicated UTI. An optimal outpatient antibiotic can be taken orally, has a tolerable side effect profile, and is concentrated to a therapeutic level in the patient’s urine. 4 Antibiotics that fit this profile are appropriate to give patients who have a low risk for infection with a multidrug resistant strain. Options for therapy include nitrofurantoin monohydrate, trimethoprim-sulfamethoxazole, fosfomycin, and pivmecillinam. 4 , 10

Recent infectious disease guidelines reflect growing concern for infection with multidrug resistant organisms. 10 When therapy needs to be escalated due to infection with a multidrug resistant organism or tissue-invasive disease with bacteremia, options remain for oral therapy. In these situations, it is advantageous to obtain urine culture and microbe antibiotic sensitivities to better eliminate the infection. If hospitalization is indicated and the patient requires parenteral antibiotics, empiric therapy should be initiated. After microorganism sensitivities return, antibiotic therapy can be narrowed to one of the following: a carbapenem, third-generation cephalosporin, fluoroquinolone, ampicillin, and gentamicin. 4

Pharmacotherapy for complicated UTIs should begin with broad-spectrum therapy and then be narrowed by sensitivities when possible. 4 The grouping which places the patient in the “complicated” category plays a role in treatment selection. For example, UTIs in men typically involve the prostate as well as the bladder, so treatment should target the infection in both organs. Patients who are pregnant require antibiotics that are safe for the fetus. 2 Some complicated UTIs, especially in the case of upper UTIs, are managed inpatient with intravenous antibiotics due to the presence of tissue-invasive disease or bacteremia. In this case, the concentration of antibiotic in the blood and the urine are important. This differs from the treatment of uncomplicated UTIs, which are dependent on the concentration of the pharmacotherapeutic agent in the urine. 4

Potential correction of modifiable risk factors for UTIs, if present, can also be addressed to prevent recurrent infection. This may include correction of an anatomic or structural abnormality of the urinary tract, consideration of alternative birth control types in a woman who uses a diaphragm with spermicide, removing a urinary catheter, or simply counseling a woman to attempt urination after sexual intercourse.

Describe Potential Complications of UTIs

Urinary tract infections can be complicated by several conditions depending on the severity and chronicity of the infection and the implicated organism. Severe upper UTIs can lead to acute kidney injury and, if not treated, can lead to permanent kidney damage and fibrosis. Similarly, upper UTIs can be complicated by renal or perinephric abscess(es). Renal abscesses are most found in patients with preexisting kidney disease. Patients infected by a urea-splitting organism are at risk of struvite stones, which are commonly found in the upper urinary tract. 4

Teaching Points

• Acute cystitis is a form of UTI and commonly presents with urinary frequency, urgency, and dysuria. Uncomplicated cases of UTIs, those seen in otherwise young, healthy, adult women, can be diagnosed by a thorough history and physical exam.
• Urinary tract infections are most often seen in sexually active, young women and older men with benign prostatic hyperplasia.
• Escherichia coli is the most implicated organism in UTIs. Other aerobic gram-negative rods and sometimes gram-positive microorganisms can be implicated, especially in patients with preexisting conditions or indwelling urinary catheters.
• Laboratory investigations, including dipstick tests, urinalysis, and urine culture, can aid physicians in the diagnosis of UTIs when needed and are important to guide effective treatment, especially in complicated UTIs.
• Uncomplicated UTIs can bet treated with outpatient oral antibiotics, with choices to include nitrofurantoin monohydrate, trimethoprim-sulfamethoxazole, fosfomycin, and pivmecillinam.
• Complicated UTIs occur in patients at higher risk of infection or in whom the infection may be difficult to treat. Some examples of patients in this category include those with anatomic or other urinary tract obstruction, catheter-associated UTIs, pregnant women, and patients who are immunosuppressed.
• Pyelonephritis is a serious upper UTI which can potentially be life-threatening if not treated promptly.
• Complications of UTIs include renal abscesses, acute kidney injury leading to chronic kidney disease, and struvite calculi.
• Broad-spectrum pharmacotherapy should be initiated for complicated microbial infections of the urinary tract. After sensitivity studies from the patient’s urine return, treatment can be narrowed to avoid the development of multi-drug resistant organisms.

Author’s Note: The opinions expressed herein are those of the author and are not necessarily representative of those of the Uniformed Services University of the Health Sciences (USUHS), the Department of Defense (DOD), or the United States Army, Navy, or Air Force.

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Patient Presentation

Ms. Smith is a 27-year-old woman who presents to her PCP after just finishing a course of antibiotics for an upper respiratory infection with complaints of dysuria and foul-smelling urine. She also complains of frequency to void, but only able to get out a few drops at a time. She has had 4/10 abdominal discomfort for the past 5 days, endorses lower back pain, and denies any hematuria with urination. She denies nausea/vomiting and denies having a fever.

Past Medical History

• Type I diabetic
• Recent use of antibiotics for URI
• History of chlamydia at age 19

Pertinent Surgical History

• No surgical history

Pertinent Family History

• Mother healthy and alive at 56 years
• Father healthy and alive at 59 years
• Sister alive and type I diabetic at age 24 years old
• Healthy 3 year old son

Pertinent Social History

• Married to husband for 5 years
• Sexually active
• Spermicide as a contraceptive method
• Physically active and attends spinning class 5 times a week