Change in urinary frequency, flow and volume - Clinical Symptoms

Change in urinary frequency, flow and volume

Urinary frequency is recorded as by day and by night so D×6, N×3 means urine is passed six times by day, with three episodes of nocturia. It is difficult to say what is normal, as individuals vary considerably, but it is important to look for changes and also to assess the degree of disruption to the individual. Nocturia more than once is probably abnormal.

·        Pregnancy is an important physiological cause of increased urinary frequency, including nocturia.

·        Associated symptoms of urgency and dysuria, usually with low volumes passed each time suggest a urinary tract infection.

·        Urgency and frequency, without dysuria, suggests urge incontinence.

·        Increased urinary volume with frequency is caused by polyuria (see below).

Urinary flow: Most individuals will empty their bladder within 30 seconds. The beginning of flow after initiation should be prompt – if delayed, this is called hesitancy, and dribbling more than a few drops after the end of micturition is called terminal dribbling. Poor flow, hesitancy and terminal dribbling are characteristic of bladder outflow obstruction, usually caused by prostatic enlargement.

Volume: The volume of urine passed is usually about 1000 to 2500 mL/day in healthy individuals. It should be approximately 500 mL less than the intake. However, in many young, active individuals who exercise (and therefore sweat) and those ‘too busy’ to drink enough fluid, this volume can often drop to ∼700–800 mL. Less than this is seen in low body mass, low salt diets, dehydration and also in acute renal failure, although often patients do not notice this. Oliguria is reduced urine excretion, often used as a term when <20 or 30 mL/hour is passed. Oliguria occurs in prerenal and renal failure. Anuria (no urine) suggests that the urinary tract is obstructed, either bladder outflow, or both kidneys, or a single functioning kidney (which will, if not rapidly treated, go on to cause postrenal failure). Polyuria is the passage of increased volumes of urine, as much as 6–8 L can be passed. Polyuria has many causes, including diabetes mellitus, diabetes insipidus, increased fluid intake and loss of urinary concentrating ability by the kidneys (which may occur in some forms of renal failure, often in the recovery phase).