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Hydronephrosis

Definition

• Robbins & Kumar Basic Pathology, p. 529

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Etiology

Causes at Each Level

• Atresia of the urethra
• Valve formations in the ureter or urethra
• Aberrant renal artery compressing the ureter
• Abnormal kidney position with torsion or kinking of ureter
• Pelviureteric junction (PUJ) obstruction - most common cause of unilateral hydronephrosis (incidence 1 in 500 live births); caused by an aperistaltic segment at the PUJ due to muscular hypoplasia, high ureteric insertion, or crossing aberrant vessels

Unilateral vs. Bilateral: Bilateral hydronephrosis occurs only when obstruction is below the level of the ureters (e.g., bladder outlet, urethra). Obstruction at or above the ureter level produces unilateral disease.

• Robbins & Kumar, p. 530; S Das Manual on Clinical Surgery, p. 582

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Pathogenesis

• Arterial insufficiency and venous stasis
• The papillae suffer the greatest pressure increase
• Initial functional disturbances are tubular (impaired concentrating ability)
• Glomerular filtration diminishes only later
• Obstruction also triggers an interstitial inflammatory reaction, eventually leading to interstitial fibrosis
• Robbins & Kumar, p. 530

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Morphology (Gross & Microscopic)

• Subtotal/intermittent obstruction: kidney massively enlarged (up to 20 cm), consisting almost entirely of the greatly distended pelvicalyceal system
• Renal parenchyma compressed and atrophied, with obliteration of papillae and flattening of pyramids
• Sudden complete obstruction: glomerular filtration compromised early, renal function may cease while dilation is still mild
• Depending on level of obstruction, ureters may also be dilated (hydroureter)

• Early: tubular dilation and atrophy
• Later: loss of glomeruli, replacement of parenchyma by fibrous tissue
• Inflammatory reaction minimal in uncomplicated cases
• Superimposed pyelonephritis is common
• Robbins & Kumar, p. 530

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Clinical Features

• Dull ache or sense of weight in the loin; may be mild enough to be mistaken for backache
• Rapid development can produce severe colicky pain
• Pain may be referred to the epigastrium (mimicking duodenal ulcer)
• Pain exacerbated by excessive fluid intake, alcohol, or diuretics
• Dietl's crisis: after a few hours of pain, passage of a large volume of urine with visible reduction in swelling

• Cystic, large renal swelling - ballottable, bimanually palpable

• Leads to anuria and renal failure
• Incomplete bilateral obstruction paradoxically causes polyuria (due to tubular concentrating defects) - this can obscure the diagnosis
• S Das Manual on Clinical Surgery, p. 582; Robbins & Kumar, p. 530

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Grading (Ultrasound)

If the hydronephrotic area demonstrates internal echoes, consider pyonephrosis (pus in the collecting system) - especially with fever and flank pain.

• False negatives in acute/partial obstruction, volume depletion, retroperitoneal fibrosis
• Renal vasculature and cysts (especially parapelvic cysts) can mimic hydronephrosis - use color Doppler to confirm flow in vessels; cysts are round and circumscribed vs. the irregular branching pattern of hydronephrosis
• Comprehensive Clinical Nephrology, 7th ed., p. 81

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Investigations

• Campbell-Walsh-Wein Urology, p. 537; S Das, p. 582

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Management

• Treat the underlying cause
• Relieve obstruction promptly to preserve renal function - removal of obstruction usually permits full return of function within a few weeks
• Longstanding obstruction produces irreversible changes

• PUJ obstruction: pyeloplasty (Anderson-Hynes dismembered pyeloplasty is the gold standard)
• Ureteric calculi: medical expulsion therapy, ureteroscopy, ESWL, or PCNL depending on size/location
• BPH/bladder outlet obstruction: alpha blockers, 5-alpha reductase inhibitors, TURP
• Malignant obstruction: ureteric stenting or percutaneous nephrostomy as temporizing measures; treat underlying malignancy
• Infected/pyonephrotic kidney: urgent nephrostomy drainage + antibiotics before definitive surgery
• Retroperitoneal fibrosis: corticosteroids, ureteric stenting, ureterolysis

Antenatal Hydronephrosis (ANH)

• Prevalence 0.6-5.4%; majority are transient and resolve after birth
• Postnatal ultrasound at least 48 hours after birth
• Diuretic renography after 4-6 weeks of life
• ANH classified into low, intermediate, and high risk
• High-risk: VCUG + antibiotic prophylaxis + functional scan + monthly follow-up
• Low-risk: 1-3 monthly US follow-up may suffice
• Bailey and Love's Short Practice of Surgery, 28th ed., p. 3451

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Complications

• Chronic renal failure (bilateral obstruction)
• Recurrent UTI / pyelonephritis
• Pyonephrosis
• Hypertension (from renal ischemia)
• Renal calculi (stasis promotes stone formation)
• Rupture of the collecting system (rare)

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Hydronephrosis: Cause-Specific Treatment

General Principles Before Specific Therapy

• Complete bilateral obstruction (or obstruction of a solitary kidney) presenting as AKI is a medical emergency - rapid intervention is required to salvage function
• Short-term obstruction (<1-2 weeks): usually adequate functional return after relief
• Chronic obstruction (>12 weeks): often irreversible and severe kidney damage; recovery may be limited even after relief
• Dialysis is rarely required except to make the patient fit for intervention (e.g., life-threatening hyperkalemia, severe fluid overload)

Key principle: Nephrostomy can be used to gauge potential for functional recovery in chronic obstruction - failure of kidney recovery after several weeks of drainage strongly suggests irreversible structural damage, making definitive surgery unlikely to benefit.

• Comprehensive Clinical Nephrology, 7th ed., p. 861-863

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Emergency / Temporizing Measures (Any Cause)

• Obstruction with infection (pyonephrosis/urosepsis)
• AKI or azotemia from obstruction of solitary or bilateral kidneys
• Severe unrelenting pain

In bilateral obstruction: place nephrostomy in the kidney with more preserved parenchyma first; bilateral nephrostomies may be required to maximize functional recovery.

• Comprehensive Clinical Nephrology, 7th ed., p. 862

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1. Pelviureteric Junction (PUJ) Obstruction

Indications for Surgery

• Functionally significant PUJ obstruction (confirmed on diuretic renography or MRU)
• Pre-operative drainage (stent or nephrostomy) only in select cases: infection, azotemia from solitary/bilateral obstruction, or severe pain

Definitive Surgery: Anderson-Hynes Dismembered Pyeloplasty

• Gold standard - success rate ~95%
• Works regardless of whether ureteral insertion is high or dependent
• Allows: reduction of redundant pelvis, excision of adynamic/dysplastic segment, preservation of crossing lower pole vessels (ureter anastomosed anterior to vessel)
• Ureter spatulated along its lateral border; anastomosis with 5-0 or 6-0 absorbable monofilament suture
• Internal ureteral stent placed routinely in adults, removed 4-6 weeks post-op
• External closed suction drain placed near (not on) suture line

Surgical Approaches (equivalent outcomes):

Alternatives (inferior outcomes):

• Endopyelotomy or balloon dilation: higher recurrence rate - outcomes inferior to open/laparoscopic pyeloplasty

Other Techniques (historical/niche):

• Y-V plasty (Foley) - for high ureteric insertion with small pelvis
• Heineke-Mikulicz reconstruction
• Davis intubated ureterotomy
• Hellstrom vascular relocation (for crossing vessel without dismemberment)
• Campbell-Walsh-Wein Urology, p. 2601-2605; Smith & Tanagho's General Urology, 19th ed.; Comprehensive Clinical Nephrology, 7th ed., p. 863

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2. Ureteral Calculi

Ureteral obstruction by papillary tissue, blood clots, or fungus ball is treated by procedures similar to those for calculi.

• Comprehensive Clinical Nephrology, 7th ed., p. 863

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3. Benign Prostatic Hyperplasia (BPH)

Conservative (Watchful Waiting)

• Patients with minimal symptoms, no infection, and normal upper urinary tract can be observed until symptoms warrant intervention

Medical Therapy

Surgical Therapy

• Comprehensive Clinical Nephrology, 7th ed., p. 863; Campbell-Walsh-Wein Urology, p. BPH chapter

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4. Carcinoma of Prostate / Bladder / Cervix / Uterus

Immediate Decompression

• PCN or retrograde ureteral stent as bridge to treatment
• Metallic stents may provide more durable decompression in malignant ureteric obstruction vs. plastic stents
• Extra-anatomic stents (tunneled percutaneously from kidney to bladder in the abdominal wall): used when conventional stents have failed or ureters are impassable due to disease

Definitive Management

• Treat the underlying malignancy (chemotherapy, radiotherapy, surgery)
• Lymphoma causing obstruction: may respond dramatically to chemotherapy alone
• Long-term stenting or nephrostomy as palliative therapy for those unfit for major surgery or incurable disease
• Ileal conduit (urinary diversion): for patients with extensive pelvic malignancy or radiation damage

A "realistic medicine" approach is important - surgical management of malignant obstruction can reduce quality of life and carries significant complication risks; patient selection is paramount.

• Comprehensive Clinical Nephrology, 7th ed., p. 863

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5. Retroperitoneal Fibrosis

In IgG4-related retroperitoneal fibrosis, corticosteroids alone may be sufficient and highly effective.

• Comprehensive Clinical Nephrology, 7th ed., p. 863

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6. Urethral Stricture

Repeated DVIU or dilation has high recurrence rates and is not a definitive solution for most strictures.

• Comprehensive Clinical Nephrology, 7th ed., p. 863

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7. Neurogenic Bladder (Spinal Cord Damage)

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8. Pyonephrosis (Infected Hydronephrosis)

1. Urgent PCN drainage (or retrograde stenting if feasible)
2. IV antibiotics covering gram-negatives (e.g., piperacillin-tazobactam or cephalosporin ± aminoglycoside)
3. Stabilize patient; treat sepsis
4. Definitive treatment of underlying cause (stone removal, stricture repair, etc.) as interval procedure once infection controlled

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9. Ureterocele

• Endoscopic incision (first-line): cystoscopic puncture/incision of the ureterocele
• May cause vesicoureteral reflux post-incision - monitor
• Open surgical reconstruction for complex or failed endoscopic cases

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10. Pregnancy-Related Hydronephrosis

• Usually physiological and transient (right side > left due to uterine dextrorotation and right ovarian vein)
• Conservative management - resolves spontaneously post-delivery
• Ureteral stent or PCN only if symptomatic obstruction with infection or significant pain

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11. Antenatal Hydronephrosis (ANH)

• Majority of ANH cases are transient and resolve spontaneously after birth
• Persistent significant hydronephrosis with confirmed PUJ obstruction and differential function <40%: pyeloplasty
• Bailey and Love's Surgery, 28th ed., p. 3450-3451

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