Urinary retention can be either acute or chronic. The most common cause of retention is outlet obstruction secondary to benign prostatic hyperplasia (BPH) in men, although medication use, acute neurologic dysfunction, urinary tract bleeding or calculi, and other anatomic obstruction are also common causes in both men and women. Acute syndromes typically present with rapid onset of lower abdominal pain occasionally radiating to the lower back. Patients typically complain of difficulty voiding but some may not volunteer this information. There is a 20% chance of a recurrence in the following 6 months after an episode of acute obstruction. Chronic obstruction usually presents with lower abdominal discomfort and the patient may note incomplete voiding or the need to void frequently. Overflow incontinence is often present.
The history should address previous episodes of obstruction, recent medication changes, and over-the-counter medicine use. Assess for any history of trauma or neurologic disability or symptoms of infection. It is critical to know if any recent urologic procedures or urinary catheterizations have been performed. The duration of symptoms is also important as it is associated with the development of postobstructive diuresis and renal dysfunction.
DIAGNOSIS AND DIFFERENTIAL
Causes of urinary retention may include anatomic obstruction, neurologic dysfunction, medication side effect, trauma to the genitourinary tract, infection, and psychological stress. Fever may indicate infection as either the cause or as a result of urinary outlet obstruction. Tachycardia and hypotension may resolve after the obstruction is relieved. The physical examination should address the functional and anatomic assessment of the lower urinary tract. Palpate the abdomen for a suprapubic mass corresponding to the distended urinary bladder. The penis should be examined for stricture at the meatus or palpable abnormalities of the penile urethra. In men the prostate should be assessed for size, texture, and tenderness. The female lower urinary tract should be evaluated for bladder prolapse or stricture of the urethral meatus. A pelvic exam is generally indicated to screen for infection or mass as a cause of obstruction. A comprehensive neurologic examination should be performed in all patients and perineal sensation and anal sphincter tone should be documented.
Bedside ultrasound can be very helpful both in distinguishing the degree of obstruction and in discriminating obstruction from the sensation of fullness associated with bladder spasm in conditions such as inflammatory or infectious cystitis. The patient should first be encouraged to attempt to void. After a voiding attempt the bladder is imaged with a low-frequency sector format probe in both the transverse and sagittal views (Figure 54-1). Many manufacturers have a calculation package available to estimate the retained urine volume. Residual volumes >50 to 150 cc are consistent with urinary retention; however, volumes in the setting of retention are typically greater than 300 cc.
Transverse and sagittal views of the urinary bladder. The prostate is visualized as a medium echogenicity ...