Page 228 - Medicine and Surgery

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224 Chapter 6: Genitourinary system

urethritis (sexually transmitted diseases causing an in- diabetes insipidus, increased fluid intake and loss of uri-
flamed urethra). nary concentrating ability by the kidneys (which may
occur in some forms of renal failure, often in the recov-
ery phase).
Change in urinary frequency, flow and
volume
Haematuria and discoloured urine
Urinary frequency is recorded as by day and by night
so D×6, N×3 means urine is passed six times by day, Haematuria is blood in the urine, which may be
with three episodes of nocturia. It is difficult to say what macrosopic or microscopic. Macroscopic haematuria is
is normal, as individuals vary considerably, but it is im- suggested by a reddish or pink discoloration of the urine,
portant to look for changes and also to assess the degree or may range to the passage of bright red, dark or even
of disruption to the individual. Nocturia more than once clotted blood. Microscopic haematuria can only be di-
is probably abnormal. agnosed by use of a ‘dipstick’ test, or on microscopy, as
Pregnancy is an important physiological cause of in- it cannot be seen by the naked eye.

creased urinary frequency, including nocturia. Blood can come from anywhere within the urinary
Associated symptoms of urgency and dysuria, usually tract, from the glomeruli, down to the urethra. Pink

with low volumes passed each time suggest a urinary tingedurineatthestartofmicturition,whichthenclears,
tract infection. suggests urethral inflammation/trauma or prostatic dis-
Urgencyandfrequency,withoutdysuria,suggestsurge ease. Haematuria that only occurs at the end of micturi-

incontinence (see page 264). tion suggests disease of the trigone of the bladder.
Increased urinary volume with frequency is caused by Whentheurineappearspink,butdoesnotcontainred

polyuria (see below). blood cells on urine microscopy, this is ‘spurious haema-
Urinary flow: Most individuals will empty their blad- turia’. If the dipstick test is positive, then this means that
der within 30 seconds. The beginning of flow after ini- there is either haemoglobin or myoglobin in the urine,
tiation should be prompt – if delayed, this is called such as occurs in rhabdomyolysis. Certain drugs (such as
hesitancy, and dribbling more than a few drops after rifampicin) and beetroot ingestion can make the urine
the end of micturition is called terminal dribbling.Poor appear orange, pink or red, but the dipstick test will be
flow, hesitancy and terminal dribbling are characteristic negative (see Table 6.1).
of bladder outflow obstruction, usually caused by pro- Darkurineshouldnotbeinterpretedas‘concentrated’,
static enlargement. asthisisanunreliablesign.Darkurinedoesoccurincon-
Volume: The volume of urine passed is usually about junction with pale stools in obstructive jaundice. Urine
1000 to 2500 mL/day in healthy individuals. It should be turns dark after standing for some time in porphyria.
approximately 500 mL less than the intake. However, in Cloudy urine has many causes, including pus (pyuria),
many young, active individuals who exercise (and there- blood (‘smoky’ urine) and phosphate crystals. A high
fore sweat) and those ‘too busy’ to drink enough fluid, concentration of phosphate in the urine is quite com-
this volume can often drop to ∼700–800 mL. Less than mon, usually completely benign, and can be reduced by
this is seen in low body mass, low salt diets, dehydration drinking plenty of fluids (not milk), but occasionally can
and also in acute renal failure, although often patients signify a tendency to develop urinary stones.
do not notice this. Oliguria is reduced urine excretion,
often used asaterm when <20 or 30 mL/hour is passed. Clinical features
Oliguria occurs in prerenal and renal failure. Anuria (no It is important to take a history, which may suggest a
urine) suggests that the urinary tract is obstructed, ei- cause:
ther bladder outflow, or both kidneys, or a single func- Dysuria suggests cystitis. This should be treated, then
tioning kidney (which will, if not rapidly treated, go on urine re-tested to ensure the haematuria has cleared.
to cause postrenal failure). Polyuria is the passage of in- Renal colic, or a previous history of urinary stones.
creasedvolumesofurine,asmuchas6–8Lcanbepassed. Recent upper respiratory tract infection suggests IgA
Polyuria has many causes, including diabetes mellitus, nephropathy or post-infectious glomerulonephritis.