Retention of urine

Retention of urine can be acute, chronic, or ''acute on chronic'. Three kinds of patient suffer from it, but the first two are much the most common: (1) The young man with a history of gonorrhoea, followed by a stricture or prostatitis. Sometimes, acute gonorrhoea alone is enough to cause retention, or he may have both. (2) The old man with a large prostate. (3) Less common, the patient with painless retention as the result of an acute neurological lesion, such as injury or tumour of his spine, in which case the signs are obvious, but are often overlooked. Retention is usually a man's problem, but it can happen in women as the result of: detrusor failure complicating pelvic surgery, especially hysterectomy (20.12D), a retroverted gravid uterus, an impacted fibroid in early labour, or a spinal lesion.

Acute retention usually presents in much the same way, whatever its cause. The patient arrives in acute discomfort, often late in the evening, when he has at last realized that he is not going to pass urine before he goes to bed. His bladder is distended to his umbilicus. If you cannot catheterize him easily, you will be wise to drain his urine suprapubically by needle aspiration. This is safer than repeatedly trying to pass a catheter (23.2). No stricture is complete, and the final cause of the obstruction is probably congestion and oedema. This will subside while his bladder drains suprapubically, so that if you try to catheterize him again a week or two later, you will probably succeed. If he has an enlarged prostate, and you can operate on him during the next few days, you can leave his suprapubic catheter in place until you do so. If he has a stricture, you can bougie him as soon as his acute obstruction is over.

SUPRAPUBIC DRAINAGE IS SAFER THAN FORCEFUL CATHETERIZATION

RETENTION OF URINE First make sure that the patient really has got retention of urine, and is not oliguric or anuric. If you cannot feel or percuss his bladder, the reason for his inability to pass urine must be in his ureters or kidneys. One glance at his face will usually tell you if his retention is acute or chronic[md]if he is in agony, it is acute. If his bladder is grossly distended, but he is in little pain, his retention is either chronic, or neurological.

Young? (probably a stricture). Old? (more likely a large prostate).

HISTORY. Has he had gonorrhoea, and how was it treated? Does he have to strain to pass urine? (suggests a stricture). Frequency, hesitancy, dysuria, nocturia? (prostatism).

EXAMINATION. Examine his urethra from end to end for a stricture, using your eyes and your fingers. Start at his glans, feel his urethra in his penis, and his perineum, for palpable thickening. Extensive strictures are associated with a large palpable area of scarring in his perineum. You may feel the distended proximal part of his urethra ending in a firm fibrous stricture. Examine his membranous urethra with your finger in his rectum. Exclude phimosis and stenosis of his meatus. Look for scars on his scrotum and perineum. If he has a painful tender area in his perineum, he probably has a periruethral abscess complicating a stricture.

Examine his prostate rectally: (1) The hardness and irregularity of (a) a carcinoma are usually easy to distinguish from the softer, smooth consistency of (b) benign hypertrophy, although the gritty feeling of (c) a calcified prostate may be misleading. (2) A firm mass above his prostate is likely to be carcinoma of his bladder. (3) Tenderness of the prostate is often difficult to assess, but a genuine prostatic abscess or acute prostatitis is usually obvious. (4) An impacted stone in the prostatic urethra (uncommon, the meatus is the common site of impaction).

CAUTION ! (1) The size of a prostate is no indication as to whether it is causing obstruction or not, but it is useful to know its size when planning surgery. (2) If his bladder is distended: (a) You will have difficulty distinguishing its base from the upper border of his prostate. (b) It may seem enlarged, because it is being pushed downwards by his distended bladder. You may find later, when he comes to operation, that his prostate has disappeared. So if you do think it is enlarged, examine him again, after you have relieved his retention[md]don't diagnose prostatic enlargement from one examination while he has retention.

Are the nerves to his bladder intact? Can he feel a pin-prick beside his anus? Test his anal reflex during rectal examination, and feel for a patulous anal sphincter. If you suspect any neurological abnormality, examine his spine and legs thoroughly.

Look for heart failure, anaemia, and hypertension, which might be the result of an obstructive uropathy.

SPECIAL TESTS. Later, examine his urine for sugar, protein, and pus. Diabetes can cause retention, and proteinuria may indicate uropathy. Measure his haemoglobin and his blood urea. Take a plain X-ray of his kidney, ureter, and bladder. There is no need for a routine intravenous urogram: reserve it for special indications, such as haematuria when the cause is not found on cystoscopy, or you suspect some abnormality of his kidneys.

RELIEVING OBSTRUCTION [s7]OF THE LOWER URINARY TACT Pass a catheter as in Section 23.2.

RECOVERY DIURESIS [s7]AND THE DANGER OF RENAL FAILURE When you have relieved an obstruction to a patient's urinary tract, his bladder and his kidneys may recover, or they may not. An early sign that his kidneys are recovering, after the relief of chronic obstruction, is a recovery diuresis, which may amount to several litres a day. He needs an adequate fluid intake, whether or not he has a diuresis.

If he has a recovery diuresis, measure his urine output carefully, and give him intravenous fluids, in large quantities if necessary. Don't forget the potassium: he may need say 35[nd]40 mmol for every litre of urine he produces. If possible, measure his serum potassium, and adjust the dose of potassium you give him accordingly. Be guided also by his pulse and blood pressure chart. If you fail to appreciate the danger of this diuresis, he may slip into renal failure again, due to dehydration leading to poor renal perfusion, in spite of an apparently normal fluid intake.

DIFFICULTIES [s7]WITH RETENTION If he has the SYMPTOMS OF PROSTATIC OBSTRUCTION with acute or chronic retention, but no large prostate, there are two possibilities (see also Section 23.20):

DYSKINESIA (formerly called bladder-neck obstruction), is a functional rather than a mechanical obstruction. You cannot diagnose it by the size of his prostate or by looking at his bladder neck. It is not mechanically tight, but fails to open up during a voiding contraction. You can easily insert a catheter, which drains quantities of urine, and cystoscopy shows trabeculation of the bladder.

BLADDER-NECK STENOSIS is a mechanical obstruction due to fibrosis or previous prostatic surgery, or schistosomiasis. As with a urethral stricture, passing a catheter is difficult or impossible. Treatment is by incising the bladder neck, if possible endoscopically, deeply enough to divide all its circular fibres.

Fig. 23-5 EMERGENCY SUPRAPUBIC PUNCTURE with a long needle is the least satisfactory of the methods described here, and is a temporary method only. Kindly contributed by Andrew Pearson.