Overview
Hydronephrosis describes the dilation of the renal pelvis and calyces that generally occurs secondary to obstruction of urine flow. Obstruction may affect one or both kidneys depending on the level of the obstruction.
Epidemiology
- Urinary obstruction is most common in the young and the old
- In men, urinary obstruction tends to be due to benign prostatic hyperplasia (BPH)
- In women, urinary obstruction tends to be due to pelvic tumours, pelvic structure prolapses, or pregnancy
Causes
Unilateral causes of hydronephrosis can be remembered using the mnemonic PACT:
- Pelvic-ureteric obstruction (e.g. malignancy)
- Aberrant renal vessels
- Calculi
- Tumours of the renal pelvis
Bilateral causes of hydronephrosis can be remembered using the mnemonic SUPER:
- Stenosis of the urethra
- Urethral valve
- Prostatic enlargement
- Extensive bladder tumour
- Retroperitoneal fibrosis
Presentation
Features depend on the duration of obstruction:
- Acute obstruction such as renal stones may present with acute, severe flank pain (renal colic)
- Chronic obstruction can present with dull abdominal pain
Other features include:
- An inability to urinate
- Recurrent urinary tract infections (UTIs) may be seen
- Lower urinary tract symptoms (LUTs):
- Decreased flow
- Urgency
- Frequency
- Incomplete emptying
- Renal angle (costovertebral angle) tenderness
- Features of a neurological disease (e.g. multiple sclerosis or spinal cord injury)
Investigations
- Urine dipstick:
- May be positive for blood, leukocytes, and/or nitrites, suggesting infection
- The presence of infection requires urgent treatment
- Urea and electrolytes (U&Es):
- May be deranged, but can be reversible with treatment
- Renal ultrasound – the first-line investigation:
- Identifies the presence of hydronephrosis
- Non-contrast CT scan:
- If renal stones are suspected
- IV pyelogram:
- Assesses the position of the obstruction
Management
If features of an infected and obstructed kidney are present, regardless of aetiology:
- 1st-line: insert a nephrostomy tube or ureteric stent
- This is to prevent renal damage and sepsis
Other management steps involve managing the underlying cause. Surgery in the form of a pyeloplasty may be considered in some scenarios.
Complications
- Sepsis and septic shock – should be suspected in any patient with fever or other signs of infection (e.g. dysuria) and hydronephrosis
- Chronic kidney disease (CKD) – continued and untreated obstructive uropathy can lead to interstitial inflammation, fibrosis, and atrophy, leading to CKD.
