What are the typical clinical manifestations and symptoms of hydronephrosis?

Hydronephrosis Symptoms

Hydronephrosis can be completely asymptomatic or present with flank pain, nausea, vomiting, hematuria, urinary tract infections, or an abdominal mass, depending on whether obstruction is acute, chronic, unilateral, or bilateral. 1, 2

Symptomatic vs. Asymptomatic Presentation

The clinical presentation of hydronephrosis varies dramatically based on the acuity and severity of obstruction:

Asymptomatic Hydronephrosis

• Most cases are now detected incidentally on imaging performed for unrelated reasons, particularly with widespread use of prenatal ultrasound and cross-sectional imaging 1, 3
• Chronic hydronephrosis can remain completely silent until significant irreversible renal damage occurs, making incidental detection both common and clinically important 1, 4
• In adults, chronic non-stone-related hydronephrosis from bladder dysfunction is frequently detected incidentally without any symptoms 1

Symptomatic Hydronephrosis

When symptoms occur, they typically include:

Pain Manifestations

• Acute flank or abdominal pain is the hallmark symptom of symptomatic hydronephrosis, particularly in urolithiasis-related obstruction 5, 2, 3
• Pain is typically sharp, begins acutely, and lasts less than 2 days in intermittent obstruction 6
• Renal colic occurs when obstruction is acute, with 49 of 50 patients with symptomatic stones demonstrating some degree of hydronephrosis 5

Associated Symptoms

• Nausea and vomiting accompany the pain in most symptomatic cases (16 of 18 patients in one series) 6, 2, 3
• Hematuria may be present, particularly with urolithiasis 2, 3
• Gastrointestinal discomfort can occur as a presenting symptom 2

Infectious Complications

• Urinary tract infections can develop, though they are relatively uncommon in uncomplicated hydronephrosis 1, 2
• Pyelonephritis may occur and requires urgent attention 2
• Pyonephrosis (infected hydronephrosis) is difficult to distinguish from simple hydronephrosis even on CT and requires urgent decompression 5, 7

Physical Examination Findings

• Palpable flank or abdominal mass was historically the most frequent finding in neonates and infants, though this is now less common due to early prenatal detection 2, 3

Age-Specific Symptom Patterns

Pediatric Population

• Most pediatric cases are now diagnosed prenatally and present without symptoms 2
• When symptomatic, children present with abdominal or flank pain, abdominal mass, hematuria, kidney stones, UTI, or gastrointestinal discomfort 2
• Less common findings include growth retardation, anemia, and hypertension 2

Adult Population

• Urolithiasis-related symptoms predominate, with renal colic being the typical presentation 1
• Intermittent pain may occur with intermittent obstruction, often triggered by increased water intake, vigorous exercise, or bladder distention 6
• Symptoms may not appear until adulthood even in congenital cases, as UPJO can be clinically silent for decades 3

Critical Warning Signs Requiring Urgent Intervention

Recognize these emergency presentations immediately:

• Bilateral hydronephrosis with elevated serum creatinine indicates impending acute kidney injury and requires urgent decompression 1, 7
• Pyonephrosis (infected obstructed kidney) requires urgent decompression before any definitive treatment 1, 7
• Symptomatic pregnancy-related hydronephrosis, particularly when anteroposterior diameter exceeds 27.5mm in the third trimester, requires intervention 8
• Posterior urethral valves in males demand urgent intervention to prevent irreversible renal damage 7

Common Clinical Pitfalls

• Do not assume absence of symptoms means absence of significant disease—chronic hydronephrosis causes progressive nephron loss even when asymptomatic 1, 4
• Always decompress a distended bladder before imaging re-evaluation, as bladder distention can cause false-positive hydronephrosis 8, 7
• Moderate to severe hydronephrosis on ultrasound in renal colic patients indicates higher risk of stone passage failure and may require more aggressive intervention 5
• Lack of hydronephrosis does not rule out ureteral stones—negative predictive value is only 65% 5