INTRODUCTION

The kidney has several vitally important functions, including the excretion of waste products and the maintenance of fluid and electrolyte balance. In addition, the kidney is an important producer of hormones, renin, vitamin D in an active form, erythropoietin and prostaglandins. Several hundred litres of plasma pass through the kidneys each day, with about 1.5 L of filtered fluid being voided as urine. Despite the fact that the kidney is a very robust organ, kidney disease is a significant and growing cause of morbidity and mortality. Kidney function deteriorates with age, but kidney disease can develop throughout life. Major risk factors are cardiovascular disease, hypertension and diabetes mellitus. Such conditions must be treated effectively in order to minimise the risk of renal damage. Early identification of kidney disease (and associated impairment) and effective treatment are essential if complications are to be avoided or at least minimised.

Certain drugs are nephrotoxic and must be either avoided altogether or given in reduced doses to patients who have a degree of renal impairment.

Although effective drugs are available for the treatment of some kidney diseases, end-stage renal failure will require some form of dialysis or perhaps renal transplantation. Renal failure has a massive impact on both the patient and his or her family due to the treatment impacting on the patient’s lifestyle (e.g. time taken up with dialysis treatments and dietary restrictions). Men are more likely to present with kidney failure than women. Black and Asian people are more likely to suffer kidney failure than white people. While some causes of kidney failure are well understood, in a number of cases (in up to 30% of patients) the cause of kidney failure cannot be found. In preventing kidney disease, there can be no doubt about the importance of keeping to a healthy lifestyle, with particular emphasis on obesity, with a consequent increased risk of developing diabetes mellitus.

Although major strides have been made in the management of kidney diseases, much remains to be done to improve the quality of life for patients with kidney failure. The kidney is a remarkable organ that has an amazing capacity to cope with many different stresses. In helping to preserve kidney function, it is essential to encourage patients to eat a healthy diet, to take suitable exercise and to stop smoking. Compliance with prescribed treatment, for example for elevated blood pressure, is extremely important. The treatment of kidney disease is essentially a team effort; it is vital to ensure the patient is a full member of the team.

ANATOMY AND PHYSIOLOGY

The prime function of the kidneys is to form and excrete urine. In so doing, water and electrolyte balance are maintained and the waste products of metabolism, urea, uric acid and creatinine are excreted. The structure of the urinary system is illustrated in Figure 18.1.

Fig. 18.1 The urinary system.

A longitudinal section of the kidney (see Fig. 18.2) indicates the structures visible to the naked eye, namely a fibrous capsule, the cortex and the medulla.

Fig. 18.2 Longitudinal section of kidney.

At the microscopic level, the kidney is made up of nephrons (see Fig. 18.3). The nephrons are responsible for maintaining fluid and electrolyte balance.

Fig. 18.3 The nephron and collecting ducts.

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