Urology treats urinary tract diseases in all genders and male reproductive issues, covering the kidneys, bladder, prostate, urethra, from infections to complex cancers.

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Diagnostic Protocol at Liv Hospital

Diagnostic Protocol at Liv Hospital

Diagnosing hydronephrosis involves several steps. The main goals are to confirm if the kidney is swollen and how severe it is, find out exactly where and what is causing the problem, and check how well the affected kidney is working. We start with simple, non-invasive tests and move to more detailed scans or functional tests if needed.

Laboratory Investigations (Blood and Urine Tests)

These tests provide crucial baseline information on overall renal function and the presence of complications such as infection or metabolic derangement.

  • Serum Creatinine and eGFR (Estimated Glomerular Filtration Rate): The primary blood markers for overall kidney function. An elevated creatinine (and low eGFR) usually suggests bilateral obstruction, obstruction in a solitary kidney, or pre-existing chronic kidney disease. Crucially, in acute unilateral obstruction, serum creatinine is often completely normal because the healthy contralateral kidney immediately compensates by increasing its own filtration rate. Therefore, a normal creatinine does not rule out severe obstruction in one kidney.
  • Urinalysis (UA) and Urine Culture: Essential to check for signs of infection (positive nitrites, leukocyte esterase, bacteria), which would escalate the case to an emergency. The presence of red blood cells (hematuria) can suggest the presence of a stone or tumor. Urine pH can offer clues to the type of kidney stone (e.g., acidic urine suggests uric acid stones; alkaline urine suggests infection stones).
  • CBC (Complete Blood Count): An elevated White Blood Cell count (leukocytosis), particularly with a “left shift” (increase in immature neutrophils), strongly suggests a severe infection, such as acute pyelonephritis or pyonephrosis.
  • Serum Electrolytes: Checked to rule out life-threatening hyperkalemia (high potassium) or metabolic acidosis, which can occur in acute bilateral obstruction or renal failure.

Imaging Modalities: Seeing the Pathology

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Ultrasound (USG) of Kidneys and Bladder

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This is the universal first-line screening tool. It is non-invasive, does not involve ionizing radiation, is relatively inexpensive, and is widely available.

  • Findings: USG uses sound waves to create images. Hydronephrosis appears as a separation of the usually bright central renal sinus echoes by a dark, anechoic (fluid-filled) branching structure representing the dilated pelvis and calyces.
  • Assessment:
    • Grading: Radiologists use the SFU grading system (1-4) to standardize severity.
    • Cortical Thickness: The thickness of the renal parenchyma is measured. Thinning suggests chronic, severe damage.
    • Bladder/Ureters: It can identify bladder distension (retention), bladder wall thickening (suggesting chronic obstruction, such as BPH), ureteroceles within the bladder, or sometimes dilated upper ureters.
    • Doppler Resistive Index (RI): Measuring blood flow resistance in renal arteries can sometimes help distinguish acute obstruction (high RI due to vasoconstriction) from chronic non-obstructive dilation.
  • Limitations: Ultrasound is very good at showing if the kidney is swollen, but it is not as good at finding out why or exactly where the blockage is. Stones in the ureter can be hard to see because of gas in the intestines. Also, ultrasound gives a still image, so it cannot tell if the kidney is blocked right now or just stretched out from an old problem that has already been fixed (see Nuclear Medicine below).
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CT Urography (CTU) - Multiphase CT Scan

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This is the gold standard imaging modality for evaluating hydronephrosis in adults. It provides a comprehensive, 3D anatomical roadmap.

  • Non-Contrast Phase: The first pass is without dye. This is the definitive test for detecting kidney and ureteral stones, with over 99% sensitivity. It shows stone size, location, and density (Hounsfield units), which guides treatment decisions.
  • Contrast Phase (Nephrographic Phase): Intravenous iodine contrast dye is injected. This phase highlights the renal parenchyma, allowing assessment of perfusion and detection of renal masses, abscesses, or areas of infarction (pyelonephritis).
  • Excretory Phase (Delayed Phase): Scans are taken 5-15 minutes later as the kidneys excrete the contrast into the collecting system. This opacifies the renal pelvis and ureters, creating a “urogram.” It is crucial for:
    • Identifying the exact transition point (the level of blockage).
    • Visualizing filling defects that are not stones, such as urothelial tumors or blood clots.
    • Defining extrinsic compression from retroperitoneal masses or fibrosis.
    • Assessing function: An obstructed kidney will show a “delayed nephrogram” (it lights up slowly and stays bright longer) and delayed contrast excretion compared to the normal side.

Magnetic Resonance Urography (MRU)

MRU is utilized primarily in specific populations to avoid the ionizing radiation of CT scans.

  • Indications: It is the preferred advanced imaging choice for pediatric patients requiring anatomical detail beyond ultrasound, pregnant women with severe symptomatic hydronephrosis, and patients with severe iodine contrast allergy.
  • Advantages: It provides superb soft-tissue contrast, making it excellent for defining complex congenital anomalies and pelvic anatomy. Functional MRU (fMRU) is an emerging technique that can also calculate GFR and drainage parameters similar to nuclear medicine.

Voiding Cystourethrogram (VCUG)

This fluoroscopic test is fundamental in pediatric urology. A catheter is placed in the bladder, which is filled with contrast dye. X-ray video is taken while the bladder fills and, crucially, while the child urinates. It is the definitive test for diagnosing Vesicoureteral Reflux (VUR) and assessing the urethra for Posterior Urethral Valves.

Functional Testing: Nuclear Medicine (Diuretic Renography)

Sometimes, an ultrasound shows a dilated kidney. Still, it is unclear if there is an active, high-pressure obstruction requiring surgery, or if it is just a “flabby,” capacious system that drains slowly but safely (e.g., a residual dilation after previous surgery or a congenital non-obstructive megaureter). Differentiating these is critical to avoid unnecessary surgery on a non-obstructed kidney. This requires a functional test.

  • Tc-99m MAG3 Scan (Mercaptoacetyltriglycine): This is the preferred isotope for evaluating obstruction, especially in kidneys with poor function. The tracer is injected intravenously, taken up by the renal tubules, and secreted into the urine. A Gamma Camera positioned over the back continuously records radioactivity counts from each kidney, generating time-activity curves.
    • Split Differential Function: The test calculates the relative contribution of each kidney to total renal function (e.g., Left: 45%; Right: 55%). A normal range is 45-55% per side. A kidney providing <10-15% of total function is often considered poorly functioning, and nephrectomy might be regarded as over-repair.
  • Diuretic Challenge (Furosemide/Lasix Protocol): About 15-20 minutes into the scan, when the renal pelvis is filled with tracer, a potent diuretic (Furosemide) is given intravenously to induce a surge in urine production. The response of the “washout curve” is analyzed:
    • Non-Obstructed pattern: The tracer is washed out rapidly from the renal pelvis after the diuretic is given. The curve on the graph drops quickly (T1/2 < 10 minutes). This indicates a dilated but non-obstructed system that does not need surgery.
    • Obstructed pattern: The tracer continues to accumulate or plateaus and does not wash out despite the diuretic surge. The curve rises or stays flat (T1/2 > 20 minutes). This indicates an actual, functionally significant obstruction that requires intervention to preserve kidney function.
  • Equivocal pattern: T1/2 between 10 and 20 minutes. This is the “gray zone” requiring clinical correlation and sometimes repeat testing.

Invasive Functional Testing: The Whitaker Test

Invasive Functional Testing: The Whitaker Test

Rarely performed today due to its invasive nature, the Whitaker test was once the gold standard. It involves placing a percutaneous needle directly into the renal pelvis and another catheter in the bladder. Saline is infused into the kidney at a fixed rate, and the actual pressure difference across the suspected obstruction point is measured directly. A pressure gradient>22 cm H2O indicates obstruction. It is reserved for highly complex, equivocal cases where nuclear scans are inconclusive.

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Assoc. Prof. MD. Hüseyin Murat Mutuş Assoc. Prof. MD. Hüseyin Murat Mutuş Urology
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FREQUENTLY ASKED QUESTIONS

Is the CT scan contrast dye dangerous for my kidneys?
Intravenous iodinated contrast dye can cause acute kidney injury known as Contrast-Induced Nephropathy (CIN), particularly in patients who already have impaired kidney function (e.g., diabetic nephropathy, CKD) or are severely dehydrated. Before ordering a contrast CT, we always check your serum creatinine and eGFR if your kidney function is below a certain safe threshold (usually eGFR < 30-45 mL/min), we will either use specialized hydration protocols to protect the kidneys, opt for a Non-Contrast CT (if looking for stones), or choose alternative imaging like Ultrasound, MRI, or a Nuclear scan, which uses different, safer tracer mechanisms.
Ultrasound is an anatomical test; it provides a static image of the kidney’s shape. It tells you, “it looks swollen.” A nuclear scan is a physiological test that shows kidney function and drainage dynamics over time. It answers the question: “Is this swollen kidney actually blocked under high pressure, or is it just a baggy, stretched-out sack that drains slowly but safely?” A kidney can remain radiographically dilated indefinitely after a stone is passed or surgery is performed, without being actively obstructed. Operating on a non-obstructed, merely dilated kidney is unnecessary surgery that entails risk without benefit. The nuclear scan provides the objective functional data needed to make the correct surgical decision.
Yes, Antenatal Hydronephrosis (ANH) is the most common anomaly detected on routine mid-trimester prenatal ultrasounds (around 18-20 weeks). It is identified by measuring the Anteroposterior Diameter (APD) of the renal pelvis. The vast majority of these cases are mild and “transient”—they are physiological or due to temporary immature ureteral peristalsis and resolve spontaneously before or shortly after birth. However, they act as an important red flag. All babies with significant antenatal hydronephrosis require a postnatal ultrasound (usually at 48 hours to 1 week of life, after newborn dehydration resolves) to rule out severe pathology like PUV, high-grade VUR, or pathological UPJ obstruction that requires early intervention to save kidney function.
In a diuretic MAG3 scan, the “Washout Curve” is the second half of the time-activity graph recorded by the computer. It represents the phase after the diuretic (Lasix) is administered. It plots the amount of radioactivity remaining in the kidney over time. A steeply downward-sloping curve indicates that the tracer is leaving the kidney rapidly, indicating good drainage (non-obstructed). A rising line, a flat plateau, or a very slowly falling line indicates the tracer is trapped in the kidney, suggesting a functional obstruction that likely requires treatment.
It can be an uncomfortable and emotionally distressing procedure for a child because it requires placing a small catheter through the urethra into the bladder. At the same time, they are awake (cooperation is needed for voiding). However, it is a quick procedure. It is absolutely crucial to perform it in indicated cases because missing a diagnosis of high-grade reflux or posterior urethral valves can lead to catastrophic, permanent kidney scarring, hypertension, and kidney failure later in life. At Liv Hospital, we use specialized pediatric protocols, the smallest possible catheters, and age-appropriate distraction techniques or mild sedation when necessary to minimize distress and make the experience as atraumatic as possible.
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