From the Guidelines
The diagnostic approach for renal and genitourinary tract disorders involves a systematic evaluation beginning with a thorough history and physical examination, followed by appropriate laboratory and imaging studies, including urinalysis, serum creatinine, blood urea nitrogen (BUN), complete blood count, basic metabolic panel, and imaging studies such as ultrasound, CT scans, and MRI, as well as functional studies like nuclear medicine scans and urodynamic studies, with the most recent and highest quality study 1 supporting the use of CT urography (CTU) as the most accurate and preferred modality for diagnosis and staging of urothelial cancer.
The initial assessment should include:
- Urinalysis to detect abnormalities like proteinuria, hematuria, or signs of infection
- Serum creatinine and blood urea nitrogen (BUN) to evaluate kidney function
- Complete blood count and basic metabolic panel to assess for anemia, electrolyte imbalances, and acid-base disorders
- Urine cultures should be obtained before starting antibiotics for suspected infections
Imaging studies are essential and typically begin with:
- Ultrasound as a non-invasive first-line option to evaluate kidney size, hydronephrosis, stones, or masses
- CT scans with or without contrast provide more detailed anatomical information for complex cases
- MRI may be preferred for specific conditions like renal masses
- Functional studies such as nuclear medicine scans can assess renal blood flow and excretory function
For lower urinary tract symptoms, the following studies may be indicated:
- Uroflowmetry
- Post-void residual measurement
- Urodynamic studies
In cases of suspected glomerular disease, the following studies provide valuable information:
- 24-hour urine collection for protein and creatinine clearance
- Kidney biopsy may be necessary for definitive diagnosis, as suggested by the KDIGO 2024 clinical practice guideline 1
The AUA/SUFU guideline on adult neurogenic lower urinary tract dysfunction 1 also recommends annual focused history, physical exam, and symptom assessment, with or without applicable questionnaires, as well as annual renal function assessment and upper tract imaging every 1-2 years for moderate-risk patients, and annual upper tract imaging and multichannel urodynamic studies for high-risk patients.
The use of CTU is supported by a meta-analysis and systematic review 1, which reported a pooled sensitivity of 96% and a specificity of 99% for identifying urothelial cancer, and a recent review by Mirmomen et al 1, which demonstrated a 91% diagnostic accuracy in detecting urothelial cancers.
In summary, a comprehensive diagnostic approach for renal and genitourinary tract disorders should include a combination of laboratory and imaging studies, with CTU being the most accurate and preferred modality for diagnosis and staging of urothelial cancer, as supported by the most recent and highest quality study 1.
From the Research
Diagnostic Approach for Renal and Genitourinary (GU) Tract Disorders
The diagnostic approach for renal and genitourinary (GU) tract disorders involves various lab and imaging tests. Some of the key tests include:
- Urinalysis to check for albuminuria, hematuria, and other abnormalities 2, 3
- Glomerular filtration rate (GFR) estimation using serum creatinine, which can be influenced by age, sex, muscle mass, and other factors 4
- Cystatin C as an alternative endogenous marker for estimating GFR, especially in cases where creatinine-based estimation may be invalid 4
- Measured GFR using an exogenous marker such as iohexol, which can provide more accurate results in certain clinical scenarios 4
- Imaging tests such as ultrasound, CT scans, and MRI to visualize the kidneys and GU tract 2, 3
Clinical Indications for Diagnostic Tests
The choice of diagnostic test depends on the clinical scenario and the suspected underlying condition. Some examples of clinical indications for diagnostic tests include:
- Extreme body composition, where creatinine-based GFR estimation may be invalid 4
- Black race, where cystatin C may be a more accurate marker for estimating GFR 4
- Disagreement between creatinine- and cystatin C-based estimated GFR (eGFR) 4
- Drug dosing, where accurate GFR estimation is crucial to avoid nephrotoxicity 4
- Liver cirrhosis, advanced chronic kidney disease, and the transition to kidney replacement therapy, where measured GFR may be necessary 4
Limitations of Diagnostic Tests
It is essential to be aware of the limitations of diagnostic tests, including: