Ross & Wilson Anatomy and Physiology in Health and Illness (165 page)

Renal cell carcinoma

Previously known as hypernephroma or Grawitz’s tumour, this tumour of tubular epithelium is more common after 50 years of age, especially in males. Clinical features include haematuria, back or loin pain, anaemia, weight loss and fever. Local spread involves the renal vein and leads to early blood spread of tumour fragments, most commonly to the lungs and bones. The causes are unknown although there is an increased incidence in cigarette smokers.

Nephroblastoma (Wilms’ tumour)

This is one of the most common malignant tumours in children under 10 years, usually occurring in the first 4 years. Clinical features include hamaturia, hypertension, abdominal pain and, sometimes, intestinal obstruction. It is usually unilateral but rapidly becomes very large and invades the renal blood vessels, causing early blood spread to the lungs.

Diseases of the renal pelvis, ureters, bladder and urethra

Learning outcomes

After studying this section you should be able to:

describe the causes and implications of urinary obstruction

explain the pathological features of urinary tract infections

outline the characteristics of the main bladder tumours

discuss the principal causes of urinary incontinence.

These structures are considered together because their combined functions are to collect and store urine prior to excretion from the body. Obstruction and infection are the main problems (
Fig. 13.25
).

Obstruction to the outflow of urine

Hydronephrosis

This is dilation of the renal pelvis and calyces caused by accumulation of urine above an obstruction in the urinary tract (
Fig. 13.25
). It leads to destruction of the nephrons, fibrosis and atrophy of the kidney. One or both kidneys may be involved, depending on the cause and site. When there is an abnormality of the bladder or urethra, both kidneys are affected whereas an obstruction above the bladder is more common and affects only one kidney. The effects depend on the site and extent of the obstruction. Stasis of urine within the urinary tract predisposes to infection.

Complete sustained obstruction

In this condition hydronephrosis develops quickly, pressure in the nephrons rises and urine production stops. The most common causes are a large calculus or tumour. The outcome depends on whether one or both kidneys are involved (homeostasis can be maintained by one kidney).

Partial or intermittent obstruction

This may progress undetected for many years. It leads to progressive hydronephrosis and is caused by, e.g.:

•
a succession of renal calculi in a ureter, eventually moved onwards by peristalsis

•
constriction of a ureter or the urethra by fibrous tissue, following epithelial inflammation caused by the passage of a stone or by infection

•
a tumour in the urinary tract or in the abdominal or pelvic cavity

•
enlarged prostate gland in the male.

Spinal lesions

When there is damage to the nerve supply to the bladder, e.g. transverse spinal cord lesions, micturition does not occur. When the bladder fills, the rise in pressure causes overflow incontinence (
p. 350
), back pressure into the ureters and hydronephrosis. Reflex micturition is usually re-established after a time, but loss of voluntary control may be irreversible. Pressure on the spinal cord and other abnormalities, e.g. spina bifida, can also impair micturition.

Urinary tract infections (UTIs)

Infection of any part of the urinary tract may spread upwards causing pyelonephritis (
p. 345
) and kidney damage.

Ureteritis

Inflammation of a ureter is usually due to the upward spread of infection in cystitis.

Cystitis

This is inflammation of the bladder and may be due to:

•
upward spread of microbes that are commensals of the bowel (
Escherichia coli
and
Streptococcus faecalis
) from the perineum via the urethra, especially in women

•
trauma, with or without infection, following health-care interventions, e.g. radiotherapy, insertion of a urinary catheter or instrument into the bladder.

The effects are inflammation, with oedema and small haemorrhages of the mucosa, which may be accompanied by
haematuria
. The sensory nerve endings in the bladder wall become hypersensitive and are stimulated before the bladder has filled, leading to
frequency of micturition
and
dysuria
. The urine may appear cloudy and have an unpleasant smell. Lower abdominal pain often accompanies cystitis. If untreated, upward spread may cause acute pyelonephritis (see
p. 345
) or septicaemia.

Cystitis is
uncomplicated
when it occurs in otherwise healthy individuals with a normal urinary tract. When it affects people with structural or functional abnormalities of the urinary tract or those with pre-existing conditions, e.g. diabetes mellitus or urinary outflow obstruction, it is described as
complicated
. Complicated UTIs sometimes cause permanent renal damage, whereas this is very rare in uncomplicated infections. Recurrence is fairly common, especially in women, either when the original infection is not eradicated or reinfection occurs.

Predisposing factors

These include stasis of urine in the bladder and the shorter female urethra, which is close to the anus (
Fig. 13.20A
), and the moist perineal conditions there that may harbour commensal microbes. Sexual intercourse may cause trauma to the urethra and transfer of microbes from the perineum, especially in the female. Hormones associated with pregnancy relax perineal muscle, and cause relaxation and kinking of the ureters. Towards the end of pregnancy, pressure caused by the fetus may obstruct the outflow of urine. In the male, prostatitis provides a focus of local infection or an enlarged prostate gland may cause progressive urethral obstruction.

Urethritis

This is inflammation of the urethra and is described in
Chapter 18
.

Tumours of the bladder

It is not always clear whether bladder tumours are benign or malignant. Tumours are often multiple and recurrence is common. Predisposing factors include cigarette smoking, taking high doses of analgesics over a long period and occupational exposure to some chemicals, e.g. aniline dyes used in the textile and printing industries.

Transitional cell carcinomas

These tumours, also known as papillomas, arise from transitional epithelium and are often benign. They consist of a stalk with fine-branching fronds, which tend to break off causing painless bleeding and haematuria. Papillomas commonly recur, even when benign. Sometimes the tumour cells are well differentiated and non-invasive but in other cases they behave as carcinomas and invade surrounding blood and lymph vessels.