Chapter 20 Urinary and male genital tracts
COMMON CLINICAL PROBLEMS FROM DISEASES OF THE URINARY AND MALE GENITAL TRACTS
Sign or symptom | Pathological basis |
---|---|
Abnormal micturition | |
Inflammation of the urethra, often accompanying a urinary tract infection | |
Obstructed urinary outflow, usually due to prostate gland enlargement | |
Incomplete bladder emptying due to obstructed urinary outflow | |
Severe obstruction to bladder outflow, usually due to prostate gland enlargement | |
Urethral discharge | Urethritis, possibly due to sexually transmitted infections (e.g. gonorrhoea) |
Scrotal swelling | |
Inflammation or ischaemia of the testis | |
Enlargement of scrotal contents due to hernia, fluid (e.g. hydrocele), varicocele or tumour | |
Genital ulceration | Often sexually transmitted infection (e.g. syphilis) |
Bone pain | If associated with male genital tract disease, possibly due to metastases from prostatic adenocarcinoma |
Raised serum prostate specific antigen | Secreted by prostatic carcinoma |
Raised serum alpha-fetoprotein and/or human chorionic gonadotrophin | Testicular germ cell neoplasia, particularly teratoma/non-seminomatous germ cell tumour |
Gynaecomastia | Possible manifestation of Leydig cell or germ cell tumour of testis |
Infertility | Impaired spermatogenesis due to endocrine disorders or to testicular lesions, or impaired ejaculation due to obstruction or to neurological disorders |
URINARY CALCULI
Calculi are classified according to their composition. The categories are:
Only 10% of patients with calcium-containing stones have hyperparathyroidism or some other cause of hypercalcaemia. However, most have increased levels of calcium in the urine, attributable to a defect in the tubular reabsorption. In the remaining patients, with idiopathic hypercalciuria, no known cause has been identified. The association of uric acid with calcium stones is probably because urates can initiate precipitation of oxalate from solution.
Uric acid stones occur in patients with gout (Ch. 7). Uric acid precipitates in acid urine. The stones are radiolucent.
RENAL TUMOURS
RENAL CELL CARCINOMA
Predisposing factors
Most cases of renal cell cancer are sporadic but there are some rare inherited disorders that predispose to development of this tumour. The most illustrative is von Hippel–Lindau (VHL) disease where there are mutations in the VHL gene, which normally produces a protein responsible for degrading proteins of the hypoxia-inducible factor (HIF) family. In the absence of this functioning protein there is accumulation of the HIF family of proteins, which in turn results in increased transcription of hypoxia-associated genes which promote cell growth, survival and angiogenesis. In VHL disease the risk of developing renal cell cancer is 70% by the age of 60 years with multiple and bilateral tumours; these patients are also at risk of epididymal, cerebral and other tumours (Ch. 26). The largest subgroup of sporadic renal cell carcinoma (clear cell carcinoma) has loss of expression of the VHL gene.
Appearances
Macroscopically, the kidney is distorted by a large tumour, found most often at the upper pole (Fig. 20.2). The cut surface reveals a solid yellowish-grey tumour with areas of haemorrhage and necrosis. The margins of the tumour are usually well demarcated, but some breach the renal capsule and invade the perinephric fat. Extension into the renal vein is sometimes seen grossly; occasionally, a solid mass of tumour extends into the inferior vena cava and, rarely, into the right atrium.
Microscopically there are distinctive different tumours with very different cytogenetic abnormalities (and by inference differing pathogenesis). Clear cell (conventional) renal cell carcinoma has VHL gene abnormalities and is the largest group. Next is papillary renal cell carcinoma which has trisomies of chromosomes 7 and 17; this has papillary structures lined by cuboidal cells and is the variant associated with acquired cystic disease in renal failure. The third largest group is chromophobe renal cell carcinoma, which has large eosinophilic cells often similar to renal oncocytoma, a benign tumour.
CARCINOMA OF THE RENAL PELVIS
The renal pelvis is lined by transitional cell epithelium and so transitional cell carcinomas can arise at this site, accounting for 5–10% of all renal tumours. As they project into the pelvicalyceal cavity, they present early with haematuria or obstruction (Fig. 20.3). Their risk factors, histology and treatment are similar to those for transitional cell carcinomas of the ureters and bladder described below.
URETERS
NORMAL STRUCTURE AND FUNCTION
The lumen is lined by urothelium; the muscle layer is predominantly circular with a thin, inner longitudinal layer, and is invested in a fibrous adventitia. The ureteric orifice is slit-like, and the course of the terminal part of the ureter through the bladder wall is oblique to form a valve (see Fig. 21.14B, p. 591).
CONGENITAL LESIONS
A congenitally short terminal segment of the ureter, which is not oblique, results in vesico-ureteric reflux, an important cause of renal infection and scarring. Hydroureter is dilatation and often tortuosity of the ureter; this condition may occur as a congenital lesion, when it is thought to reflect a neuromuscular defect. The most frequent causes of hydroureter in the adult are low urinary obstruction and pregnancy.
BLADDER CALCULI
Diverticula, obstruction and inflammation are all important in the development of stones within the bladder. Alternatively, calculi may be passed down the ureter from the kidney. Bladder stones may be asymptomatic, but eventual chronic irritation and infection lead to frequency, urgency, dysuria and sometimes haematuria. There is an increased risk of bladder carcinoma; this is often of squamous type, arising from metaplastic squamous epithelium.
TUMOURS OF THE BLADDER
TRANSITIONAL (UROTHELIAL) CELL CARCINOMA OF THE BLADDER
Appearances
At presentation most bladder tumours are low-grade and papillary, with fronds lined by a slightly thickened urothelium showing little cytological abnormality (Fig. 20.4). Usually there is no invasion of the lamina propria. Papillary tumours are frequently multiple, consistent with a widespread field change throughout the urothelium including the upper tract, even though it is histologically normal.
Prognosis and treatment
Prognosis is closely related to the stage of the tumour. Superficial tumours (without muscle invasion) can be removed by transurethral resection and have an excellent prognosis. These patients are likely to have a field change and so require regular follow-up cystoscopy as about 70% of patients will develop further tumours. Progression to more invasive tumours occurs in around 20% of patients. Intra-vesical treatment with BCG or chemotherapy can be used for multiple superficial tumours or carcinoma in situ. Tumours which have invaded muscle require more intensive therapy. A radical cystectomy will remove the tumour and all the dysplastic bladder epithelium but it is a large operation which results in the patient having an ileal bladder, either isotopic or with a stoma. Radiotherapy is another possible treatment modality.
PROSTATE GLAND
NORMAL STRUCTURE AND FUNCTION
The prostate gland surrounds the bladder neck and proximal urethra (Fig. 20.5). It consists of five lobes, separated by the urethra and ejaculatory ducts. Two lateral lobes and an anterior lobe enclose the urethra. The two lateral lobes are marked by a posterior midline groove, palpable on rectal examination. The middle lobe lies between the urethra and ejaculatory ducts and the posterior lobe lies behind the ejaculatory ducts. The normal gland weighs about 20g and is enclosed in a fibrous capsule.
Individual glandular acini have a convoluted outline, the epithelium varying from cuboidal to a pseudostratified columnar cell type depending upon the degree of activity of the prostate and androgenic stimulation. The epithelial cells produce prostate-specific antigen (PSA), acid phosphatase and the prostatic secretion that forms a large proportion of the seminal fluid for the transport of sperm. The normal gland acini often contain rounded concretions of inspissated secretions (corpora amylacea). The acini are surrounded by a stroma of fibrous tissue and smooth muscle.
INCIDENCE OF PROSTATIC DISEASE
The principal clinicopathological features of the common types of prostatic pathology are compared in Table 20.1.
PROSTATITIS
In addition, there are patients with granulomatous inflammation of the prostate.
Granulomatous prostatitis
Granulomatous prostatitis is a heterogeneous group of lesions, all of which may cause enlargement of the gland and urethral obstruction. The inflammatory component and associated fibrosis produce a firm, indurated gland on rectal examination which may mimic a neoplasm clinically, thus highlighting the importance of correctly diagnosing this uncommon group of conditions.
BENIGN PROSTATIC HYPERPLASIA
Morphology
The hyperplastic process usually involves both lateral lobes of the gland. In addition, there may be a localised hyperplasia of peri-urethral glands posterior to the urethra and projectinginto the bladder adjacent to the internal urethral meatus (Fig. 20.6). This hyperplasia is described as ‘median’ lobe enlargement but does not correspond to the anatomical middle lobe.
The cut surface of the enlarged prostate shows multiple circumscribed solid nodules and cysts (Fig. 20.7). Histological examination reveals two components: hyperplasia both of glands and of stroma. The acini are larger than normal (some may be cystic) and are lined by columnar epithelium covering papillary infoldings (Fig. 20.8). The acini may contain numerous corpora amylacea. Phosphates and oxalates may be deposited around these to form prostatic calculi.
Clinical features
There are four main factors in the development of obstructive symptoms:
The resulting obstruction to the bladder outflow produces various lower urinary tract symptoms (LUTS), which can be grouped as bladder sensation symptoms, storage symptoms and voiding symptoms; these have been incorporated into an International Prostate Symptom Score. Bladder sensation may be normal, increased or decreased. Storage symptoms include daytime frequency, nocturia, urgency and incontinence. Voiding symptoms include hesitancy, poor or intermittent stream, straining and dribbling.
Complications
Continued obstruction of the bladder outflow results in gradual hypertrophy of the bladder musculature. Trabeculation of the bladder wall develops due to prominent bands of thickened smooth muscle between which diverticula may protrude. This compensatory mechanism eventually fails, with resulting dilatation of the bladder. The ureters gradually dilate (hydroureter), allowing reflux of urine; if untreated, bilateral hydronephrosis may develop, with dilatation of renal pelvis and calyces (Fig. 20.9).