on 22-Feb-2022 (Tue)

ally the reverse of the chain rule for differentiation

rearrange the integrand as a function of something times the derivative of that same something,

In men, AUR is most often secondary to benign prostatic hyperplasia (BPH); AUR is rare in women [2,3].

The most common mechanisms are outflow obstruction, neurologic impairment, or an inefficient detrusor muscle [9,10]. Other causes include medications, infection, and trauma

In males, the most common cause of obstruction is benign prostatic hyperplasia (BPH) [2-5,11]. Other causes of outflow obstruction in men include constipation, prostate or bladder cancer, urethral stricture, urolithiasis, phimosis, or paraphimosis [4,13].

In females, obstruction is generally secondary to anatomic distortion, including pelvic organ prolapse (eg, cystocele or rectocele), pelvic masses, or, less commonly, urethral diverticulum [7,14-23].

AUR can occur with spinal cord injuries from trauma, infarct or demyelination, epidural abscess and epidural metastasis, Guillain-Barré syndrome, diabetic neuropathy, and stroke [13]

AUR may occur in patients with an inefficient detrusor muscle when a precipitating event results in an acute distended bladder (eg, with a fluid challenge, during general or epidural analgesia without an indwelling catheter) [9,13,24-26]. This most often occurs in patients with obstructive urinary symptoms at baseline.

Multiple medications (table 1) are implicated as a cause of urinary retention; most common among these are the anticholinergic and sympathomimetic drugs [27].

Infections may lead to AUR in the setting of inflammation that causes obstruction. For example, an acutely inflamed prostate gland from acute prostatitis can cause AUR, particularly in men who already have BPH [11,29]. Similarly, a urinary tract infection can cause urethritis and urethral edema resulting in AUR [1,29].

Genital herpes may cause AUR both from local inflammation as well as sacral nerve involvement.

Other infections that have been associated with AUR include varicella zoster and vulvovaginitis [1,11,29].

AUR may also occur postoperatively or in the postpartum period.

Acute urinary retention (AUR) generally presents as an inability to pass urine, usually associated with lower abdominal and/or suprapubic discomfort [13]. Affected patients are often restless and may appear in considerable distress. In older adult patients, particularly those with dementia or other forms of cognitive impairment, AUR may present as an acute change of mental status [30].

These manifestations may be less pronounced when AUR is superimposed upon chronic urinary retention. Chronic urinary retention is often painless [31]. Acute-on-chronic urinary retention may present with overflow incontinence. The patients may complain of incontinence rather than the inability to pass urine.

The patient history should focus on previous history of retention or lower urinary tract symptoms (table 2), prostate disease (hyperplasia or cancer), pelvic or prostate surgery, radiation, or pelvic trauma. The patient should also be asked about the presence of hematuria, dysuria, fever, low back pain, neurologic symptoms, or rash. Finally, a complete list of medications (including over-the-counter medications (table 1)) should be obtained

Younger patient age, a history of cancer or intravenous drug abuse, and the presence of back pain or neurologic symptoms suggest the possibility of spinal cord injury or compression.

The initial physical examination should include lower abdominal palpation. The urinary bladder may be palpable, either on abdominal or rectal examination. Deep suprapubic palpation will provoke discomfort.

In patients whose history and physical examination strongly suggest a diagnosis of AUR, or those in acute distress, it is reasonable to proceed directly to catheterization, which is both diagnostic and therapeutic, rather than waiting to obtain a bladder ultrasound. Alternatively, a bladder scanner can be used if immediately available.

A bladder volume on ultrasound ≥300 cc suggests urinary retention warranting decompression. However, the bladder ultrasound may be inaccurate due to body habitus, tissue edema, or prior surgery and scarring. If the patient is in discomfort and unable to void, a urethral catheter should be placed regardless of the estimated volume on bladder ultrasound.

Upon placement of a urethral catheter, the initial amount of urine drained should be noted. Patients with volumes <200 cc likely do not have acute urinary retention. These patients should undergo further evaluation by a urologist in an outpatient setting.

In patients with AUR of unknown etiology, further physical examination should include the following:

• Rectal examination – A rectal examination should be done in both all patients to evaluate for masses, fecal impaction, perineal sensation, and rectal sphincter tone. A normal prostate examination does not preclude benign prostatic hyperplasia (BPH) as a cause of obstruction.

• Pelvic examination – Women with urinary retention should have a pelvic examination.

• Neurologic evaluation – The neurologic examination should include assessment of strength, sensation, reflexes, and muscle tone.

A urine sample should be obtained and sent for urinalysis and urine culture.

The need for other laboratory testing should be determined based upon findings from the patient's history and physical examination. Most patients who present to the emergency department with concern for urinary retention have serum chemistries and creatinine checked. These should be checked in any patient whose history suggests acute-on-chronic urinary retention to evaluate for renal failure.

Other labs that may be helpful include a complete blood count (CBC) for suspected infection. We do not check a prostate-specific antigen (PSA) as it is expected to be elevated during an episode of AUR.

A 14 to 18 gauge French catheter should be inserted as first-line in most patients with AUR [11]. Indications for choosing a smaller or larger catheter are discussed below.

For patients with an initial urine volume of less than 200 cc, immediate catheter removal and subsequent observation for recurrence is usually appropriate. These patients should be evaluated for other causes of abdominal and/or suprapubic discomfort.

For patients with greater than 200 cc of urine, the volume drained in the first 10 to 15 minutes should be noted and recorded as it is useful for subsequent management regarding duration of catheter use. If this volume exceeds 400 cc, the catheter is typically left in place. For volumes less than 400 cc, the decision to leave the catheter in place is guided by the clinical scenario.

For patients with greater than 200 cc and less than 400 cc, the decision on catheterization may take into account multiple factors. Patient comorbidities, mental status, ability to return to the hospital, and numerous other factors may influence this decision to leave an indwelling catheter.

In patients with AUR, we generally leave the catheter in place for three to five days, after which the patient is given a voiding trial. Examples of earlier catheter removal include postoperative patients who are initially unable to void but recover this ability within a few hours.

Urethral catheterization is contraindicated in patients who have had recent urologic surgery (eg, radical prostatectomy or urethral reconstruction), and these patients should have suprapubic catheterization. (See 'Suprapubic catheter' below.)

Although there is a theoretical risk to placement of a urethral catheter in the setting of acute bacterial prostatitis, these patients may have an attempt at gentle urethral catheterization by an experienced clinician.

Some patients may have an obstruction that does not readily allow passage of the catheter. A partially obstructing urethral or prostatic scar may be present if the patient has had a prior transurethral procedure (eg, transurethral resection of the prostate), or pelvic trauma or radiation [10]. In this case, the obstruction may be bypassed by downsizing the catheter to a 10 or 12 gauge French indwelling catheter. In the absence of prior instrumentation or injury, the more common cause of obstruction would be an enlarged prostate. In this case, a larger catheter (20 or 22 gauge) with a firm coude tip may be needed and may require urologic consultation.

Placement of a suprapubic (SP) catheter is sometimes necessary in patients who have contraindications to or fail urethral catheterization (eg, those with recent urologic surgery, acute prostatitis, urethral stricture disease, severe benign prostatic hyperplasia [BPH], or other anatomic abnormalities).

In cases when no urologist or appropriately trained clinician is available and the patient is in distress, bladder distention can be temporarily relieved with suprapubic aspiration via a needle. However, this treatment can make subsequent SP placement more difficult or even dangerous due to bladder decompression. If an appropriately trained medical professional will be available in the near future, needle decompression should be deferred.

We recommend complete drainage of the bladder in patients with AUR. At one time, rapid complete bladder decompression was thought to increase the rate of potential complications (transient hematuria, hypotension, and postobstructive diuresis). However, partial drainage and clamping does not reduce these complications and may increase risk for urinary tract infection [31,34-36]

Hematuria occurs in 2 to 16 percent of patients but is rarely clinically significant [31]. For example, one trial found that hematuria occurred in approximately 11 percent of patients with AUR; hematuria resolved with irrigation for almost all patients [37].

After initial bladder decompression, patients may experience a transient hypotension [31]. However, blood pressure usually normalizes without intervention and does not progress to clinically significant hypotension.

Relief of urinary tract obstruction can lead to a postobstructive diuresis, which is defined as a diuresis that persists after decompression of the bladder. A postobstructive diuresis is primarily a problem with chronic, not acute, urinary retention and usually represents an appropriate attempt to excrete excess fluid retained during the period of obstruction [38].

The majority of patients can be safely managed as an outpatient once the bladder is decompressed [39]. Hospitalization is indicated for patients who have urosepsis, have obstruction related to malignancy, or acute myelopathy [11]. Patients with associated acute renal failure also require hospitalization [1].

The duration of catheterization depends on the underlying etiology for AUR. Patients with an underlying etiology that is being treated and expected to resolve (eg, urinary tract infection) should attempt a voiding trial as soon as possible that condition has been treated to avoid catheter complications.

In other patients who have underlying etiologies not likely to resolve (eg, spinal cord injury) and/or who have acute-on-chronic urinary retention, catheterization may become chronic. Those patients may benefit from either long-term clean intermittent catheterization (CIC) or SP placement.

Clean intermittent catheterization — CIC has fewer complications compared with indwelling urethral and SP catheterization. In patients with AUR, compared with indwelling catheters, CIC is associated with an increased rate of spontaneous voiding and reduction in urinary tract infections [40].

CIC may be a reasonable option in hospitalized patients where nursing care is available and AUR is expected to resolve in a short period of time. CIC is also a reasonable option for outpatients who are comfortable with managing the catheter and patients with acute-on-chronic urinary retention who are expected to require long-term catheterization (eg, prior spinal cord injury).

If the etiology for AUR is not found on initial evaluation, patients should be referred to a urologist to evaluate for less common anatomic etiologies (eg, urethral stricture or urethral diverticulum) and/or for possible bladder function testing. Urodynamic studies should be performed by a urologist with experience in functional bladder disorders.

Medical management — In men with BPH or presumed BPH, we recommend initiating an alpha-1-adrenergic antagonist (eg, alfuzosin 10 mg) at the time of initial catheterization. We also suggest ongoing treatment with an alpha-1-adrenergic blocker and a 5-alpha reductase inhibitor to delay the recurrence of AUR.

Alpha-1-adrenergic antagonists function to relieve the mechanical obstruction associated with BPH by relaxation of the smooth muscle at the bladder neck and the prostatic capsule [42]. A 2014 systematic review of nine randomized trials evaluating alpha-1-adrengeric antagonists prior to the removal of urethral catheters for AUR found moderate evidence that alpha-1-adrenergic antagonists increase success rates of trials without a catheter (relative risk [RR] 1.55, 95% CI 1.36-1.76) with low incidence of adverse effects [43].

5-alpha reductase inhibitors (eg, finasteride and dutasteride) decrease the incidence of AUR in men with BPH but do not reduce the early recurrence of AUR [49-51]. Patients need to be treated for more than one year to prevent AUR and reduce the need for surgery.

Initial bladder decompression and initiation of medical therapy should be followed by a TWOC. We suggest that patients have two trials prior to considering surgical therapy. We generally have patients attempt a TWOC one to two weeks after the catheter is placed. While a second TWOC for patients who fail the initial trial has a lower rate of success than the initial TWOC, for patients who fail the initial TWOC, we suggest a second trial of TWOC after an additional two weeks with the catheter.

In our office, a voiding trial starts with catheter removal early in the morning, either at home or in the office. Patients are encouraged to hydrate aggressively and to return to the office in the early afternoon for a postvoid residual (PVR). A PVR over 400 cc is generally considered a failure, under 200 cc would be a success, and PVRs between 200 to 400 cc result in a risk benefit discussion of options. If the patient is unable to void or if they are voiding with high PVRs, they are offered instruction in clean intermittent catheterization. If they are unable or unwilling to do this, a catheter is placed.

Reported success rates for initial TWOC in men with prostate disease with AUR have ranged from 20 to 40 percent [45]. Factors that favor a successful TWOC include age less than 65 years, detrusor pressure greater than 35 cm H₂O, a drained volume of less than one liter at catheterization, and the identification of a precipitating event [41,45].

The optimal duration of catheter management in men with BPH prior to a trial of voiding has been evaluated, with contradictory findings. Randomized trials found an increase in the likelihood of spontaneous voiding when catheters were removed at seven days rather than immediately or after two days [52,53]. However, an observational study in 2600 men with AUR found that men who were catheterized for three days or less had greater success with spontaneous voiding compared with men catheterized for more than three days [54]. Two limitations of this observational study include the potential for greater underlying comorbidity in the men who were catheterized longer; and that 80 percent were treated with an alpha-1-adrenergic antagonist.

Men who fail a second TWOC may require surgical therapy. Surgical therapy remains the definitive treatment of AUR. Among symptomatic patients with BPH, transurethral resection of the prostate (TURP) reduces the risk of developing AUR by 85 to 90 percent [55].

We evaluate all patients being considered for surgical intervention following an episode of AUR with urodynamic studies, to determine whether retention is directly related to outlet obstruction, with concomitant elevation in bladder pressures, or to an inefficient bladder muscle. Patients with bladder impairment are unlikely to benefit from a surgical procedure aimed to reducing outlet resistance.