B27. Urinary obstruction and stasis: Differential diagnosis and management
Urinary tract obstruction (UTO) is when there is blockage of urine anywhere in the urinary tract. It may be acute or chronic, and it may be unilateral or bilateral. We can also distinguish upper UTO from lower based on whether it occurs at the level above or below the bladder, respectively. The obstruction may be complete (no urine can pass) or incomplete. UTO may cause (postrenal) acute kidney injury and, if left untreated, chronic kidney disease.
UTO may cause hydronephrosis or hydroureter, which refers to dilation of the renal collecting system or the ureter, respectively. These may be visualised on ultrasound and are signs of UTO. Stasis of urine due to UTO also predisposes to urinary tract infection.
Etiology
- By location
- Upper urinary tract obstruction (supravesical)
- Nephrolithiasis or ureterolithiasis
- Urothelial cancer (bladder or ureter or renal collecting system)
- Sloughed papilla (from renal papillary necrosis)
- Stricture
- Blood clots (from surgery, instrumentation, or malignancy)
- Lower urinary tract obstruction (infravesical)
- Kidney stone in the urethral orifice
- Urethral stricture
- BPH
- Prostate cancer
- Any cancer located in the pelvis
- Posterior urethral valve
- Neurogenic bladder
- Blood clots (from surgery, instrumentation, or malignancy)
- Upper urinary tract obstruction (supravesical)
- By age group
- Children – congenital abnormalities
- Posterior urethral valves
- Ureteropelvic junction obstruction
- Strictures
- Adults – nephrolithiasis
- Elderly – BPH, prostate cancer, any cancer located in the pelvis or retroperitoneum
- Children – congenital abnormalities
Clinical features
Upper UTO (and by extension, hydronephrosis and hydroureter) is usually painless and asymptomatic, but there may be pain related to the underlying cause of the obstruction, usually only if caused by stone. In case of bilateral upper UTO or lower UTO the patient may have noticed anuria or oliguria.
If the UTO has caused AKI or CKD, symptoms from these may occur eventually.
Chronic partial lower UTO can cause lower urinary tract symptoms.
Diagnosis and evaluation
Ultrasound is the primary modality in the evaluation of urinary tract obstruction as it can measure the volume of the bladder and the size of the ureters and renal collecting system to look for an overfilled bladder, hydroureter, and hydronephrosis, respectively. Ultrasonography may also show signs of a stone if present. If stone is suspected but cannot be visualised on ultrasonography, CT is the gold standard.
If there is infravesical obstruction and a lot of urine has collected in the bladder, it can sometimes be palpated.
Labs should be taken to look for abnormal kidney function tests.
Management
UTO should be relieved urgently. The manner of which to relieve it depens on the location of the obstruction. If there is signs of urinary tract infection due to the obstruction, relief of the obstruction is urgent.
A supravesical obstruction should be relieved with a ureteric stent or percutaneous nephrostomy. Infravesical obstruction with a bladder catheter, either transurethral catheter (first choice) or a suprapubic catheter.