Chronic Renal Failure
Chronic renal failure implies long-standing, and usually progressive, impairment in renal function. In many instances, no effective means are available to reverse the primary disease process. Exceptions include correction of urinary tract obstruction, immunosuppressive therapy for systemic vasculitis and Goodpasture's syndrome, treatment of accelerated hypertension, and correction of critical narrowing of renal arteries causing renal impairment. A good deal, however, can be done to slow the rate of deterioration in renal function otherwise to be expected.
Wide geographical variations in the incidence of disorders causing chronic renal failure exist. For example, the most common cause of glomerulonephritis in sub-Saharan Africa is malaria. Schistosomiasis is a common cause of renal failure due to urinary tract obstruction in parts of the Middle East, including southern Iraq.
These disorders are seen in the UK only in those who have resided in endemic areas. The incidence of end-stage renal failure varies between racial groups, as does the relative importance of different causes of chronic renal failure. For example, end-stage renal failure is three to four times as common in black Africans in the UK and USA as it is in whites, and hypertensive nephropathy is a much more frequent cause of end-stage renal failure in this group.
The prevalence of diabetes mellitus and hence of diabetic nephropathy is higher in some Asian groups than in whites. The age group involved is also of relevance. For example, chronic renal failure due to atherosclerotic renal vascular disease is much more common in the elderly than in the young.
History of Chronic Renal Failure
Particular attention should be paid to:
- duration of symptoms
- drug ingestion, including non-steroidal anti-inflammatory agents, analgesic and other medications, and unorthodox treatments such as herbal remedies
- previous medical and surgical history, e.g. previous chemotherapy, multisystem diseases such as SLE
- previous occasions on which urinalysis or measurement of urea and creatinine might have been performed, e.g. pre-employment or insurance medical examinations, new patient checks
- family history of renal disease.
Symptoms of Chronic Renal Failure
The early stages of renal failure are often completely asymptomatic, despite the accumulation of numerous metabolites. Serum urea and creatinine concentrations are measured in renal failure since methods for their determination are available and a rough correlation exists between urea and creatinine concentrations and symptoms. These substances are, however, in themselves not particularly toxic. The nature of the metabolites which are involved in the genesis of symptoms is unclear. Such metabolites must be products of protein catabolism (since dietary protein restriction may reverse symptoms associated with renal failure) and many of them must be of relatively small molecular size (since haemodialysis employing membranes which allow through only relatively small molecules improves symptoms). Little else is known with certainty.
Symptoms are common when the serum urea concentration exceeds 40 mmol/L, but many patients develop uraemic symptoms at lower levels of serum urea. Symptoms include:
- malaise, loss of energy
- loss of appetite
- insomnia
- nocturia and polyuria due to impaired concentrating ability (bed-wetting in children may be a result of nocturia rather than emotional disturbance)
- itching
- nausea, vomiting and diarrhoea
- paraesthesiae due to polyneuropathy
- 'restless legs' syndrome (overwhelming need to frequently alter position of lower limbs)
- bone pain due to metabolic bone disease
- paraesthesiae and tetany due to hypocalcaemia
- symptoms due to salt and water retention - peripheral or pulmonary oedema
- symptoms due to anaemia
- amenorrhoea in women; erectile impotence in men.
The kidneys themselves are usually impalpable unless grossly enlarged as a result of polycystic disease, obstruction or tumour. Rectal and vaginal examination may disclose evidence of an underlying cause of renal failure, particularly urinary obstruction, and should always be performed.
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