eMedicine Specialties > Emergency Medicine > Genitourinary
Urinary Obstruction: Treatment & Medication
Updated: Jan 29, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Prehospital Care
Pulmonary edema as a consequence of renal failure from complete urinary obstruction should be treated conventionally. Partial obstruction can cause significant defects in salt and water retention, resulting in hypovolemia, which responds to standard fluid administration protocols.
Emergency Department Care
Prior to addressing the specific therapy for obstruction, the ED physician must investigate and begin treatment of the life-threatening complications of obstructive uropathy (eg, pulmonary edema, hypovolemia, urosepsis, hyperkalemia).
- The overriding goal in the treatment of urinary obstruction is the reestablishment of urinary flow. As stated previously, the longer the obstruction exists, the lower the rate of renal recovery and the lower the GFR if any recovery occurs.
- Once urinary obstruction is entertained in the differential diagnosis, a transurethral bladder catheter should be placed.
- A properly positioned Foley catheter can be diagnostic as well as therapeutic for obstruction below the level of the bladder.
- If no urine is obtained, the proper placement of the Foley should be tested by catheter irrigation. If fluid returns freely, the catheter tip is probably in the bladder and obstruction above the bladder should be investigated.
- If a question still remains, imaging studies such as radiography and ultrasonography also may be used to establish proper Foley placement.
- If a large PVR volume is noted, obstruction below the bladder should be investigated.
- Catheter drainage should then be maintained until the etiology of the obstruction is treated appropriately.
- Intermittent clamping of the Foley is recommended to prevent symptoms of hypotension and hematuria often ascribed to rapid bladder decompression.
- Hypotension after bladder decompression is thought to be due to a vagolytic response from a rapid change in bladder-wall tension.
- In a series of patients with obstruction, Christensen et al found a 50% decrease in intravesical pressure after only the first 100 mL of urine was removed.2 Since the major drop in bladder pressure occurred with the early removal of relatively small amounts of urine, they concluded that fractionating urine removal in bladder obstruction was unjustified.
- Hematuria and bladder spasm is another well-known complication of bladder decompression. Gould et al compared the incidence of hematuria in rapidly emptied and gradually emptied obstructed dog bladders.3 They found that hematuria was correlated strongly with the degree of bladder wall damage prior to relief of obstruction and was not correlated with the rate of emptying.
- Urine should be drained completely and rapidly from an obstructed bladder. Prolonged urine stasis only predisposes the patient to UTI, urosepsis, and renal failure.
- Calculi are the most common causes of unilateral ureteral obstruction.
- More than 90% of renal calculi less than 5.0-7.0 mm in size pass spontaneously. Obstruction in these cases can be treated conservatively with intravenous fluids and analgesia.
- Surgical drainage is necessary only for patients with unrelenting pain, UTI, or persistent obstruction.
- Position of the stone in the ureter determines the preferred method of removal.
- Calculi in the renal pelvis and proximal ureter are amenable to nephroscopy and removal under direct visualization.
- Percutaneous nephrostomy drainage is used for midureteral stones.
- Distal ureter stones can be removed cystoscopically by the use of a loop or basket.
- Extracorporeal shock wave lithotripsy is another viable option for stones in any position in the ureter.
- Bilateral obstruction of the ureters is almost always an asymmetric process.
- Generally, whatever the etiology of ureteral obstruction, one ureter is obstructed slowly and asymptomatically over a long period of time.
- Not until the second ureter is obstructed are symptoms of renal failure, hyperkalemia, or acidosis observed.
- In this condition, radionucleotide scanning can be helpful in identifying the most viable kidney for drainage.
- For midureteral or proximal ureteral obstruction, percutaneous nephrostomy tube placement is indicated.
- For distal obstruction, cystoscopic placement of a ureteral stent can be attempted.
- Cases of renal recovery have been detected by radionucleotide scan in kidneys without renal blood flow.
- In case of suspected urosepsis from bilateral ureteral obstruction, bilateral percutaneous nephrostomy tubes must be placed to ensure that both potentially infected systems are drained.
- Intrarenal obstruction secondary to crystals or protein casts is not amenable to surgical drainage. Maintenance of adequate hydration to promote high rates of urine output to dilute crystals and casts is the main treatment.
Consultations
- Consult a urologist when a transurethral catheter cannot provide adequate bladder drainage. Filiform catheters or a suprapubic cystotomy may be required to drain the bladder completely. Invasive pyelography for higher-level obstructions can be diagnostic and therapeutic.
- Consult a nephrologist to provide emergent hemodialysis if necessary.
Medication
Medical therapy for benign prostate hypertrophy (BPH) has provided a very successful alternative to surgical therapy, whose risks include anesthesia, infection, impotence, incontinence, consistent failure to restore normal flow, and frequent necessity for retreatment.
Medical therapy should not be offered to individuals presenting with absolute indications for surgical intervention.
Indications for surgical prostatectomy are recurrent urinary retention, recurrent UTIs, renal insufficiency, bladder calculi, and recurrent gross hematuria.
Alpha1-adrenoceptor antagonists
The rationale for alpha-blockers in the treatment of BPH is based on the fact that smooth muscle accounts for 40% of the hypertrophied prostatic mass. The basal tone of prostatic smooth muscle is increased significantly by stimulation of alpha1-adrenergic receptors. Alpha-blockers relieve bladder obstruction from BPH by decreasing tonic contraction of prostatic smooth muscle.
Recent molecular studies have identified 3 subtypes of alpha1 receptors. The alpha1-AR subtype is specific for prostatic smooth muscle. Tamsulosin is a selective alpha1-AR antagonist. Recently, a new alpha1-AR antagonist, silodosin (Rapaflo), was approved.
Prazosin (Minipress)
Treats prostatic hypertrophy. Improves urine flow rates by relaxing smooth muscle. This relaxation produced by blocking alpha1-adrenoceptors in bladder neck and prostate. When increasing dosages, give first dose of each increment at bedtime to reduce syncopal episodes. Although doses >20 mg/d usually do not increase efficacy, some patients may benefit from doses as high as 40 mg/d.
Adult
2 mg PO bid
Pediatric
Not established
Acute postural hypotensive reaction from beta-blockers may worsen; indomethacin may decrease antihypertensive activity; verapamil may increase serum levels and may increase patient's sensitivity to prazosin-induced postural hypotension; may decrease antihypertensive effects of clonidine
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in renal insufficiency; dizziness or drowsiness may occur after first dose (avoid driving or performing hazardous tasks for first 24 h after taking this medicine or when dose increased); orthostatic hypotension may occur
Terazosin (Hytrin)
Quinazoline compound that counteracts alpha1-induced adrenergic contractions of bladder neck, facilitating urinary flow in presence of BPH.
Adult
5 mg or 10 mg PO qd
Pediatric
Not established
NSAIDs decrease effects; diuretics and antihypertensive medications increase effects
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in renal impairment; may cause marked hypotension following first dose or coadministration with beta-blockers
Tamsulosin (Flomax)
Selective alpha1-antagonist for treatment of BPH.
Adult
0.4 mg or 0.8 mg PO qd
Pediatric
Not established
With coadministration of warfarin, monitor PT time and BP closely; cimetidine may increase effects (especially with tamsulosin doses >0.4 mg); other alpha-adrenergic blocking agents may increase toxicity
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Evaluate prior to start of therapy to rule out carcinoma of prostate; adverse effects include postural hypotension, dizziness (caution in driving, operating machinery, or performing hazardous tasks); instruct patients not to crush, chew, or open capsules
Alfuzosin (UroXatral)
Alpha1-adrenoceptors blocker in the prostate. Blockade of adrenoceptors may cause smooth muscles in bladder neck and prostate to relax, resulting in improvement in urine flow rate and reduction in symptoms of BPH.
Adult
10 mg PO qd
Pediatric
Not established
Effects may increase with coadministration of diuretics and antihypertensive medications
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Dizziness, fatigue, and headache may occur; patients should avoid situations where injury could result if syncope occurs; rule out presence of carcinoma of prostate before beginning therapy
Silodosin (Rapaflo)
Selectively antagonizes postsynaptic alpha1-adrenergic receptors in prostate, bladder base, prostatic capsule, and prostatic urethra. This action induces smooth muscle relaxation and improves urine flow. Indicated for signs and symptoms of benign prostatic hyperplasia.
Adult
8 mg PO qd with food
CrCl 30-50 mL/min: 4 mg PO qd
Pediatric
Not established
Coadministration with strong CYP3A4 inhibitors (eg, itraconazole, clarithromycin, ritonavir) or P-glycoprotein inhibitors (eg, cyclosporine) increases serum levels; concurrent use with other alpha-blockers may increase effect; coadministration with antihypertensive agents may increase incidence of dizziness and orthostatic hypotension
Documented hypersensitivity; severe renal impairment (ie, CrCl <30 mL/min); severe hepatic impairment (ie, Child-Pugh score >10); coadministration with strong CYP3A4 inhibitors
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Risk of postural hypotension and resulting symptoms (eg, dizziness, syncope); caution with moderate renal impairment; may cause intraoperative floppy iris syndrome during cataract surgery; may cause retrograde ejaculation
More on Urinary Obstruction |
| Overview: Urinary Obstruction |
| Differential Diagnoses & Workup: Urinary Obstruction |
 Treatment & Medication: Urinary Obstruction |
| Follow-up: Urinary Obstruction |
| References |
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References
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Further Reading
Keywords
urinary obstruction, obstruction of the urinary tract, blocked urine flow, renal failure, kidney failure, renal dysfunction, kidney dysfunction, renal insufficiency, renal calculi, urinary tract infection, UTI, renal tubular acidosis, RTA, hyperkalemia, hypomagnesia, hypophosphatemia
