Emergency Department Care
Initial management and catheterization
Partial obstruction can cause significant defects in salt and water retention, resulting in hypovolemia, which responds to standard fluid administration protocols. Before 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). Pulmonary edema as a consequence of renal failure from complete urinary tract obstruction should be treated conventionally.
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. [12] 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. [13] 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.
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.
Calculi
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.
Acute renal colic due to ureteral stone obstruction is an emergency that requires immediate pain management. Medical expulsive therapy (MET), usually with α-receptor antagonists, can facilitate stone passage and reduce the need for analgesia. [14]
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.
Location of obstruction
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.
Complications
Postobstructive diuresis is an uncommon but clinically significant complication following the release of urinary obstruction. It is characterized by a marked natruresis and diuresis with excretion of large amounts of sodium and water.
In addition to the potential for severe volume depletion, electrolyte disorders such as hypokalemia, hyponatremia, hypernatremia, and hypomagnesemia may occur. The etiology of this massive diuresis and electrolyte loss is multifactorial. It is related to fluid and urea overloads during obstruction and acquired tubular resistance to antidiuretic hormone and aldosterone.
Treatment of postobstructive diuresis consists of judicious fluid replacement with 0.45% saline (at a rate slightly less than urine output) and replacement of electrolytes. Urinary tract infections may occur due to urinary stasis. Additionally, instrumentation may also introduce contamination. Antibiotic selection depends on the age, sex, and comorbid conditions of the patient. Additionally, minimizing drug interactions, such as patients on anticoagulation, should also guide antibiotic selection.
Acute urinary retention has been reported following photoselective vaporization (PVP) to treat benign prostatic obstruction. Risk factors for this complication include adenoma volume lower than 40 mL, lower lasting time, international prostate symptoms score (IPSS) ≥19, and previous treatment with 5-alpha-reductase inhibitors. [15]
