Introduction

UA is one of the most commonly ordered diagnostic tests in obstetrics and gynecology.¹ It plays key roles in routine prenatal care, in infection monitoring, and in evaluating genitourinary complaints, such as dysuria, gross hematuria, or suprapubic pain.² Not only is it low cost, but it also has a rapid turnaround time, which allows for the test results to directly influence decisions around screening, diagnosis, and referral in the acute care setting.³ However, beyond its use in identifying UTIs or monitoring proteinuria during pregnancy, urinalysis offers a wealth of additional information that is often overlooked. Specific findings may indicate systemic disease, renal pathology, or complications warranting further evaluation.¹ This review aims to go beyond the basics by exploring advanced interpretations, including lesser‑focused parameters, pitfalls, and indications for clinical referral to support ob-gyn providers in translating UA findings into practical care decisions.

Microscopy vs dipstick analysis

It is important to draw attention to the minor differences between urinalysis performed by dipstick vs formal microscopy. Typically, urine microscopy is completed by a laboratory after the sample is sent out. Depending on the specific laboratory, results are often available within 24 hours, providing clear data for interpretation before formal urine culture results are available. Although a urine dipstick can be performed instantaneously at the bedside or in office spaces, microscopy offers significant advantages over dipstick, including visualization and quantification of red blood cells, white blood cells, bacteria, epithelial/squamous cells, crystals, and casts.

Urine collection technique

The clinical utility of urinalysis depends on proper specimen collection. In most settings, a clean-catch midstream urine sample is recommended to minimize contamination from vaginal secretions, skin flora, and menstrual blood. Patients should be instructed to cleanse the urethral opening, begin voiding into the toilet, and collect the midstream portion in a sterile container.⁴ Samples should ideally be analyzed within 2 hours of collection, as delays can lead to bacterial overgrowth, changes in pH, and degradation of cellular elements.⁵ Certain UA findings may suggest contamination or improper collection. Numerous squamous epithelial cells, mixed bacterial flora without a dominant organism, or isolated leukocyte esterase positivity without symptoms often indicate contamination rather than a true infection.³ When contamination is suspected, repeating the urinalysis with proper collection technique or as a catheterized collection is recommended before pursuing additional workup or specialty referral.

Basic UA parameters

Protein

Proteinuria on urinalysis reflects increased glomerular permeability and may indicate underlying renal or systemic disease.¹ UA samples are typically reported as graded values by mg/dL: negative (less than 10 mg/dL), trace (10-20 mg/dL), 1+ (30 mg/dL), 2+ (100 mg/ dL), 3+ (300 mg/dL), or 4+ (1g/dL). However, exact ranges may differ by laboratory or dipstick manufacturer. Transient proteinuria, often due to fever, exercise, or dehydration, is defined as proteinuria less than or equal to 2+ that is absent on 2 to 3 repeated samples within a month.³ Persistent proteinuria, characterized by greater than 2+ protein detected on 2 to 3 repeated samples within a month, warrants further evaluation with a urine protein-to-creatinine ratio (UPCR), which must be ordered separately as it is not included in a standard urinalysis. A UPCR of at least 0.3 typically confirms persistent proteinuria and may prompt a 24-hour urine collection for further quantification.³

In pregnancy, proteinuria is a diagnostic component of preeclampsia and may even precede the onset of hypertension. The American College of Obstetricians and Gynecologists (ACOG) recommends checking for proteinuria at the initial prenatal visit and during evaluations for hypertensive disorders.^1,6 Outside of pregnancy, proteinuria may also be seen in UTIs, particularly when accompanied by symptoms such as dysuria or pelvic pain.² However, this finding is nonspecific and should be interpreted within the broader clinical picture. Persistent proteinuria (2 to 3 samples in one month) should prompt primary care referral, whereas highly concerning findings, such as 4+ protein with the presence of casts (see casts section) or proteinuria, should prompt consideration for a nephrology referral.⁷

Blood (hematuria)

Hematuria indicates the presence of red blood cells (RBCs) in the urine and can be either visible (gross) or detectable only by microscope (microscopic). An office dipstick UA will result in a positive (trace to 1+ or greater) for peroxidase activity of RBCs; however, quantifying the number of whole RBCs is not possible without microscopy. Typically, hematuria is characterized as 3 or more RBCs per high-power field on microscopic evaluation of a urinary sediment per American Urological Association (AUA) guidelines.⁸

ACOG defines microscopic hematuria more conservatively in low-risk women (premenopausal, nonsmokers, younger than 50 years old, no visible blood) as greater than 25 RBC/hpf.⁹ Hematuria may result from a UTI, nephrolithiasis, menstruation, trauma, glomerular disease, or malignancy. Gross hematuria is associated with malignancy in up to 30% to 40% of cases and warrants full urologic evaluation, whereas microscopic hematuria is most often benign, particularly in premenopausal women, and is commonly due to infection, stones, trauma, or menstruation.¹⁰ It is recommended that the initial evaluation focus on identifying and addressing reversible and benign causes such as infection or menstruation. Often, obtaining a catheterized specimen in women can help differentiate between vaginal and rectal sources. If hematuria persists after these are ruled out, repeat urinalysis and further testing may be needed based on patient risk factors.¹¹

Obtaining urine microscopy is useful in determining the source, as findings such as dysmorphic red blood cells or red cell casts suggest glomerular disease and should prompt nephrology referral, whereas normal red cells with no proteinuria suggest lower urinary tract sources. Ultimately, evaluation should be systematic, starting with exclusion of benign causes and proceeding based on risk profile to guide urologic or nephrology referral.¹²

Leukocyte esterase and nitrites

Leukocyte esterase, an enzyme produced by white blood cells (WBCs) on urinalysis, reflects the presence of WBCs in the urine and is a marker of pyuria, which often indicates inflammation or a UTI. Nitrates are normally present in urine as a result of dietary intake, whereas nitrites are formed when certain gram-negative bacteria reduce urinary nitrates into nitrites. Accordingly, nitrites, not nitrates, are the analyte detected on urine dipstick testing and are clinically relevant for UTI screening.

Although a positive nitrite result is highly specific for a bacterial UTI, not all uropathogens produce nitrites, and the test can be falsely negative if the urine hasn’t been in the bladder long enough.¹³ Although the presence of nitrites is more specific for an active UTI, leukocyte esterase is generally more sensitive. However, when both tests are positive, the likelihood of a UTI increases, especially when interpreted alongside clinical symptoms and other UA findings, such as the presence of blood or protein.¹⁴

The combination of positive leukocyte esterase, nitrites, and Gram stain (presence of gram-positive or -negative bacteria) has been reported to have a 87.6% sensitivity and 94.6% negative predictive value for the UTI detection.¹⁵ Positive leukocytes can be seen in isolation without nitrates or infection in noninfectious cystitis, sometimes called sterile pyuria, and may warrant urologic referral.¹⁶

Glucose and ketones

Glucose in the urine, or glycosuria, typically occurs when plasma glucose levels exceed the renal threshold, usually around 180 mg/dL to 200 mg/dL, and is most commonly associated with uncontrolled diabetes mellitus.^3,17 UA dipstick results provide estimated orders of magnitude of glucose presence: 1+ (100mg/dL), 2+ (300mg/ dL), and 3+ (1000mg/dL), specifically based on the manufacturer. However, during pregnancy, physiologic changes such as increased glomerular filtration and lower renal threshold can lead to transient glycosuria, even in the absence of hyperglycemia.¹⁸ Urinary ketones reflect increased fat breakdown and can be seen in states such as diabetic ketoacidosis, prolonged fasting, vomiting, pregnancy, or other catabolic conditions.^3,17 In the absence of another clear explanation, the presence of both findings should prompt evaluation for metabolic or endocrine disorders.

pH and specific gravity

Urine pH provides insight into a patient’s acid-base balance and can be affected by diet, metabolic disturbances, or infections with urease-producing organisms such as Proteus, which make the urine more alkaline. Specific gravity reflects urine concentration or dilution. A low specific gravity (less than 1.003) signifies maximum dilution, often due to high fluid intake, and should be interpreted in the context of hydration status and other findings (ie, glucose). A high value (greater than 1.020) may be due to dehydration or conditions such as syndrome of inappropriate antidiuretic hormone secretion that cause the body to retain water. Increased specific gravity can be due to high values of protein and ketones and should also be evaluated in context to other parameters.¹⁷

Underappreciated UA parameters

Bilirubin

Finding bilirubin in the urine is always abnormal and typically indicates an issue with the liver or bile ducts. This is because only conjugated bilirubin, which is water soluble, can be excreted in urine. As a result, when bilirubin levels accumulate in the bloodstream, it suggests that the liver is not functioning properly or that an obstruction is preventing its normal flow into the intestines. Therefore, the presence of urinary bilirubin can be an early sign of conditions such as hepatocellular dysfunction, cholestasis, and biliary obstruction, and should prompt further investigation into hepatic health.^3,17 From an ob-gyn standpoint, urinary bilirubin deserves particular attention in scenarios such as intrahepatic cholestasis of pregnancy, where impaired bile flow leads to bilirubin buildup; hemolysis, elevated liver enzymes, and low platelets syndrome; or preeclampsia with liver involvement, which can compromise hepatic function, and drug-induced liver injury from medications commonly used in pregnancy.^19,20

Urobilinogen

Urobilinogen forms from intestinal conversion of bilirubin and is normally present in small amounts (0.2-1mg/dL). Increased urinary urobilinogen can indicate hemolytic processes or hepatocellular disease, whereas absent or low urobilinogen suggests complete biliary obstruction or antibiotic use. Both elevated (>2+) and absent levels are clinically significant and should prompt assessment for hemolysis or biliary pathology.

Casts

The presence and type of urinary casts can offer important clues about underlying renal pathology. Visualization of casts is only available with microscopy and is one of that procedure’s benefits over dipstick analysis. Casts are cylindrical structures formed in the renal tubules and can vary in composition depending on what is trapped in the matrix. Hyaline casts, made from Tamm-Horsfall protein, are often nonspecific and can be seen in healthy individuals, especially during dehydration, exercise, or fever, but may also appear in chronic kidney disease. RBC casts are pathognomonic for glomerulonephritis, whereas WBC casts are suggestive of interstitial nephritis or pyelonephritis. Epithelial casts, which contain renal tubular cells, are associated with acute tubular necrosis but may also be seen in concentrated urine. Granular casts form from the breakdown of cellular elements and are commonly seen in acute tubular injury. Waxy casts indicate more severe or chronic renal disease, such as advanced chronic kidney disease or acute kidney injury. Lastly, fatty casts, containing lipid-laden cells, are highly suggestive of nephrotic syndrome.^3,17 It is important to recognize these patterns, especially when evaluating pregnant patients with concerns for preeclampsia, lupus nephritis, or other renal complications. The presence of casts should trigger referral to primary care or nephrology.

Crystals

Crystals in the urine may be benign or indicate underlying pathology, which can be incredibly helpful in ob-gyn patients with symptoms such as flank pain or recurrent UTIs. Visualization of crystals is only possible with microscopy.³ Some crystals, such as calcium oxalate and uric acid, are relatively common and can be seen in healthy individuals, especially with concentrated or acidic urine. Calcium oxalate crystals, which appear as envelope- or dumbbell-shaped, may also be associated with high oxalate intake, nephrolithiasis, or ethylene glycol ingestion. Uric acid crystals, often diamond- or needle-shaped, are typically seen in urine with a pH lower than 5.5 and may suggest urate nephrolithiasis or acute urate nephropathy. Less commonly, certain crystals can point to underlying disease; cystine crystals, which are hexagonal, are seen in acidic urine and indicate cystinuria, a rare genetic condition. Triple phosphate (struvite) crystals, shaped like coffin lids, form in alkaline urine and are linked to UTIs caused by urease-producing organisms such as Proteus or Klebsiella.¹⁷ Noting the presence and type of crystals can help guide further workup for renal, metabolic, or infectious causes, depending on the clinical context.

When to refer

Certain UA findings, especially when the clinician can confirm proper collection technique, should prompt specialty referral, particularly when persistent or paired with abnormal clinical symptoms. As outlined throughout this review, proteinuria should prompt a nephrology evaluation to assess for glomerular disease or chronic kidney dysfunction.^1,7 Similarly, the presence of red blood cell casts or persistently abnormal specific gravity may reflect underlying tubular or glomerular pathology, also warranting nephrology involvement.³

Hematuria is another key trigger for referral. Microscopic hematuria, defined as at least 3 RBCs per high-power field on microscopic evaluation of a single, properly collected urine specimen, should prompt further evaluation when persistent, particularly in patients older than 50 years or those with risk factors for malignancy. Gross hematuria during pregnancy or suspected obstructive nephrolithiasis should lead to prompt urologic consultation.¹⁰

Bilirubinuria or elevated urobilinogen, especially when accompanied by abnormal liver enzymes, pruritic, or right upper quadrant discomfort, may indicate hepatobiliary dysfunction or pregnancy-specific conditions such as ICP and warrant hepatology or maternal-fetal medicine referral.²⁰ Endocrinology input is appropriate when UA reveals recurrent glucosuria or ketonuria, particularly in patients with known or suspected diabetes mellitus or diabetic ketoacidosis.³ As discussed, these findings, though individually nonspecific, gain diagnostic value when integrated with symptoms, pregnancy status, and trends over time.

Conversely, not all abnormal UA findings necessitate referral. Mild, transient leukocyte esterase or nitrite positivity may resolve with empiric treatment, especially in the context of a UTI. Isolated abnormal pH values or occasional crystals are often benign and influenced by hydration status or dietary intake.^3,17 It is also important to understand that false positives can occur from medications, diet, exercise, contamination, and improper testing techniques. Nonetheless, providers should be aware of which parameters consistently signal pathology requiring further workup.

Table 1 summarizes key UA findings that should raise concern and trigger subspecialty evaluation, aligning with the clinical decision points discussed throughout this review.

Common pitfalls

One of the most common errors in urinalysis interpretation is overreliance on dipstick results without confirmatory urine microscopy. This can lead to misclassification of conditions such as hematuria, proteinuria, or UTI. The literature consistently emphasizes that dipstick findings for blood and protein require microscopic confirmation or quantitative testing, as false positives are not uncommon and can lead to unnecessary referrals or missed diagnoses.³ False positives are due to factors such as menstrual blood, semen, or oxidizing agents.^12,21 Improper collection technique, such as failure to obtain a clean-catch midstream sample, can introduce contamination from vaginal flora, skin, or the environment, which then compromises the accuracy of the results.⁴

Conclusion

Urinalysis remains a vital and accessible tool in obstetric and gynecologic care. When interpreted systematically and with attention to both common and underappreciated parameters, it can aid in identifying renal, urologic, and hepatobiliary conditions. By recognizing patterns in urine findings and integrating them with the clinical context, ob-gyn providers can improve diagnostic accuracy, initiate earlier specialist involvement, and ultimately enhance patient outcomes.

References:

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