Retención Urinaria: Fisiopatología y Manejo

Notas del editor

1. Acute urinary retention is the sudden, painful inability to urinate spontaneously despite having a distended bladder central to the diagnosis is the presence of a large volume of urine, which when drained by catheterization, leads to resolution of the pain What represents large has not been strictly defined, but volumes of 500-800ml are typical
2. Elderly men are at highest risk (10%-30% 5-year)because there is an age-associated increase in benign prostatic enlargement resulting from benign prostatic hyperplasia, the most common cause of obstructive acute urinary retention
3. Multiple causative factors operate via 3 main mechanisms: obstructive, neurogenic, and detrusor underactivity. More than 1 mechanism might exist in a single patient.
4. 18% de los casos diseminados o localmente avanzados de carcinoma prostático debutan como una R.A.O. Constipation or fecal impaction is the most common reversible cause of geriatric acute urinary retention
5. agonistas alfa-adrenérgicos, anticolinérgicos, neurolépticos y antidepresivos tricíclicos (alteran el control neurológico de la micción), y los antagonistas del calcio e inhibidores de prostaglandinas (disminuyen la capacidad de contracción del detrusor), Anticholinergic and nonsteroidal anti-inflammatory drugs decrease bladder contractility; sympathomimetics increase smooth muscle tone in the prostate and bladder neck causing intrinsic obstruction.3 Opiates impair autonomic function, and diuretics increase urine production leading to bladder overdistention
6. Paradoxic incontinence is loss of urine due to chronic urinary retention or secondary to a flaccid bladder. The intravesical pressure finally equals the urethral resistance; urine then constantly dribbles forth.
7. Comorbidities and polypharmacy can alter the presentation, complicate the diagnosis and treatment, and increase the morbidity and mortality in acute urinary retention.
8. Physical examination should include abdominal palpation and percussion to detect the distended bladder and abdominal masses. The penis should be examined for phimosis, paraphimosis, edema, urethral strictures, foreign bodies, discharge, and malfunctioning catheters. Rectal examination might detect fecal impaction, prostate enlargement or nodules, prostatitis, rectal masses, or abnormal sphincter tone.3,7 Neurologic examination can identify central, peripheral, or spinal cord abnormalities.
9. prostate-specific antigen might be elevated in acute urinary retention irrespective of the cause.3 Even when not acutely informative, baseline values for prostate-specific antigen (drawn before the acute urinary retention or after resolution) correlate with prostate volume and are predictive of acute urinary retention Bladder and kidney ultrasonography can establish the diagnosis of acute urinary retention with less discomfort and fewer complications than an in-and-out catheterization, identifying bladder stones and tumors, bladder compression from masses, and hydronephrosis. Cystoscopy will evaluate urethral strictures, gross hematuria, and bladder tumors or stones. Urodynamic testing of the detrusor and sphincter muscles is needed when obvious reversible causes have been eliminated, there is coexisting neurologic disease, multiple explanations for acute urinary retention are discovered, there is a history of lower urinary tract procedures, or prostatic resection is under consideration
10. Elderly patients with acute urinary retention frequently have precipitating events (eg, pneumonia, stroke) that require hospitalization, whereas acute urinary retention itself might precipitate or exacerbate comorbid medical conditions (eg, dementia with delirium) necessitating inpatient care. Hospitalization also is indicated when renal failure, urosepsis, causative malignancy, or spinal cord compression is identified, or for patients unable to manage a urinary catheter at home
11. Although inherently more invasive, suprapubic catheters can be necessary in patients with urethral stricture, recent urologic instrumentation, or benign prostatic hyperplasia who fail the initial trial without a catheter and are poor surgical candidates. There is conflicting evidence regarding the relative incidence of bacteruria and infection between urethral and suprapubic catheters.
12. para facilitar la entrada de la sonda, se debe traccionar suavemente del pene, con lo que se evita la formación de pliegues de la mucosa uretral, y es imprescindible completar su introducción hasta el pabellón a pesar de que pueda salir orina previamente
13. Men with acute urinary retention from benign prostatic hyperplasia have an increased chance of returning to normal voiding if alpha blockers are started at the time of catheter insertion Precipitated retention often does not recur; spontaneous retention often does. 50% with spontaneous retention will experience a second episode of retention within the next week or so, and 70% within the next year. One study identified 3 days as ideal in acute urinary retention/benign prostatic hyperplasia, with longer periods associated with more adverse events and lower success rates.8 Successful spontaneous voiding is achieved in 23% to 40% on the first attempt at catheter removal,1 whereas an additional one quarter will have a successful second attempt. Alpha-1 receptor blockers provide rapid symptom relief from outlet obstruction caused by benign prostatic enlargement and delay the time to acute urinary retention; however, they do not decrease the overall risk of acute urinary retention or surgery (ie, they do not decrease prostate volume).5,6 Initiation of alpha blockade 2 to 3 days before catheter withdrawal increases the probability of return to spontaneous voiding.3,8 Their most common adverse effects are postural hypotension and dizziness,5 which are serious concerns in elderly men because of associated falls. Initiation at lower doses, slow dose titration, and use of more selective agents (eg, tamsulosin and alfuzosin) reduce these risks
14. Patients may require careful monitoring for postobstructive diuresis (>200 mL/hour) after establishing drainage, particularly if obstruction was prolonged and blood urea nitrogen (BUN) and creatinine are significantly elevated Relief of longstanding obstruction may result in major hematuria secondary to bladder mucosal disruption Significant hypotension may occur secondary to a vasovagal response or may be caused by relief of pelvic venous compression from bladder distention.
15. The pressure within a tense, obstructed bladder is sensitive to small changes in volume; the pressure begins to fall after the removal of only 5 to 15 mL, and is reduced by approximately 50 percent with the removal of 100 mL, and by 75 percent with the removal of 250 mL of fluid [27,28] . Therefore, barring the clinically unrealistic strategy of frequent release of very small urine volumes, a rapid fall in bladder pressure is not preventable. Although postobstructive diuresis, hypotension, and hematuria from rapid urinary bladder decompression can occur, these are rarely clinically significant, and no evidence suggests that gradual decompression is safer
16. Hospitalization is indicated for patients who are uroseptic or have obstruction related to malignancy or spinal cord compression