Obstructive uropathy – acute and chronic medical management

Table 1 Causes of urinary tract obstruction by anatomical level

Level of urinary tract obstruction	Causes
Upper tract (kidney, ureter)	Calculi
	Tumour
	Upper tract bleeding (e.g., bleeding renal cancers, traumatic)
	Anatomic abnormality (e.g., pelvi-ureteric junction obstruction)
	Papillae sloughing (e.g., pyelonephritis, tuberculosis)
	Ureteric stricture
	Ureterocoele
Lower tract (bladder, prostate, urethra)	Calculi
	Tumour
	Neurogenic bladder
	Benign prostatic hyperplasia
	Prostatitis
	Cystocoele
	Bleeding (i.e., clot retention)
	Urethral stricture
	Posterior urethral valves
Extrinsic	Retroperitoneal fibrosis
	Aneurysm
	Pregnancy
	Faecal impaction
	Pelvic organ prolapse
	Phimosis

Table 2 Common perioperative considerations and medical therapies for obstructive uropathy

Medication class	Comments
Perioperative care
Non-steroidal anti-inflammatory drugs	Should be avoided or used cautiously in any form of acute or chronic kidney disease
	There is ample experimental and clinical evidence suggesting that non-steroidal anti-inflammatory drugs (NSAIDs) may worsen kidney function in patients with renal impairment, especially during a concomitant physiologic insult, and delay renal recovery from acute kidney injury (AKI)[33-36]. NSAIDs interfere with renal auto-regulation and can directly induce de novo AKI through several mechanisms.
Antihypertensives	Hypertension is frequently seen in patients with obstructive uropathy, due to volume expansion and upregulation of renin and erythropoietin release because of focal hypoxia[37,38]
	Hypertension may reverse rapidly following acute relief of obstruction and diuresis, so antihypertensive medications should be rationalised accordingly
	Renin-angiotensin system blockade, with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, should be avoided or prescribed carefully due to the well-recognised risks of pre-renal AKI and hyperkalaemia
Antibiotics	Leucocytosis and raised inflammatory markers are commonly seen in acute presentations of urinary tract obstruction as part of the stress response. A low threshold for empiric antimicrobial coverage for urinary infection is prudent
	Renal drug clearance declines roughly in proportion to the drop in GFR. Antibiotic dosing or frequency may need to be reduced, depending on the agent. Antibiotics considered ‘nephrotoxic’ may need to be withheld, such as vancomycin and gentamicin
	Urosepsis in the context of an obstructed collecting system is tissue-invasive. Therefore, selected antibiotics must be broad-spectrum and penetrant, and reach therapeutic levels quickly. Intravenous ampicillin or ceftriaxone are typical choices, which can be modified based on culture sensitivities
Obstructive uropathy pharmacologic therapies
Alpha-1 adrenergic receptor antagonists	Common uses: Benign prostatic hyperplasia, urolithiasis (medical expulsive therapy)
	Rationale: Induce smooth muscle relaxation, thereby enlarging ureteral and urethral calibre and improving flow
	Examples: Prazosin (non-selective), tamsulosin (selective), silodosin (selective)
5-alpha reductase inhibitors	Common uses: Benign prostatic hyperplasia
	Rationale: Targeted antiandrogen effect, thereby reducing prostate volume and the static component of bladder outlet obstruction
	Examples: Dutasteride, finasteride
	Combination tablets with alpha-1 adrenergic receptor antagonists are also widely available
Phosphodiesterase-5 inhibitors	Common uses: Benign prostatic hyperplasia, erectile dysfunction
	Rationale: Exact mechanism of action in lower urinary tract symptoms is unclear but may antagonise phosphodiesterase (PDE) receptors on smooth muscle cells, thus inducing urethral relaxation and improved urine flow, or increase bladder and prostate perfusion Examples: Sildenafil, tadalafil, vardenafil
	PDE-5 inhibitors are commonly prescribed for men with erectile dysfunction and coexisting features of prostatism.
	PDE-5 inhibitors may also be used in combination with alpha-1 adrenergic receptor antagonists or 5-alpha reductase inhibitors