ABC of Kidney Disease

David Goldsmith, Satish Jayawardene, Penny Ackland, David Goldsmith, Satish Jayawardene, Penny Ackland

• Publisher: BMJ Books
• Year: 2013
• ISBN:
  9781118493731
• Edition: 2
• Topic: Médecine
• Subtopic: Néphrologie

ABC of Kidney Disease

ABC of Kidney Disease, Second Edition

The ABC of Kidney Disease, Second Edition is a practical guide to the most common renal diseases to help healthcare professionals screen, identify, treat and refer renal patients appropriately and to provide the best possible care.

Covering the common renal presentations in primary care, this highly illustrated guide provides guidance on symptoms, signs and treatments, which tests to use, measures to prevent progression, and when and how to refer. Fully revised in accordance with current guidelines, it also includes organizational aspects of renal disease management, dialysis and transplantation. The appendices contain an explanatory glossary of renal terms, guidance on anaemia management and information on drug prescribing and interactions.

The ABC of Kidney Disease, Second Edition is an ideal practical reference for GPs, GP registrars, junior doctors, medical students and for anyone working with patients with renal-related conditions.

About the ABC series

The new ABC series has been thoroughly updated, offering a fresh look, layout and features throughout, helping you to access information and deliver the best patient care. The newly designed books remain an essential reference tool for GPs, GP registrars, junior doctors and those in primary care, designed to address the concerns of general practitioners and provide effective study aids for doctors in training.

Now offering over 70 titles, this extensive series provides you with a quick and dependable reference on a range of topics in all the major specialities. Each book in the new series now offers links to further information and articles, and a new dedicated website provides you with even more support.

The ABC series is the essential and dependable source of up-to-date information for all practitioners and students in general practice.

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Chapter 1

Diagnostic Tests in Chronic Kidney Disease

Behdad Afzali¹, Satish Jayawardene² and David Goldsmith¹

¹King's College London, London, UK

²King's College Hospital NHS Foundation Trust, London, UK

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Overview

• Urinary protein excretion of <150 mg/day is normal (∼30 mg of this is albumin and about 70–100 mg is Tamm-Horsfall (muco)protein, derived from the proximal renal tubule). Protein excretion can rise transiently with fever, acute illness, urinary tract infection (UTI) and orthostatically. In pregnancy, the upper limit of normal protein excretion is around 300 mg/day. Persistent elevation of albumin excretion (microalbuminuria) and other proteins can indicate renal or systemic illness.
• Repeat positive dipstick tests for blood and protein in the urine two or three times to ensure the findings are persistent.
• Microalbuminuria is an early sign of renal and cardiovascular dysfunction with adverse prognostic significance.
• Non-visible haematuria (NVH) is present in around 4% of the adult population—of whom at least 50% have glomerular disease.
• If initial glomerular filtration rate (GFR) is normal, and proteinuria is absent, progressive loss of GFR amongst those people with NVH of renal origin is rare, although long-term (and usually community-based) follow-up is still recommended.
• Adults aged 40 years old or more should undergo cystoscopy if they have NVH.
• Any patient with NVH who has abnormal renal function, proteinuria, hypertension and a normal cystoscopy should be referred to a nephrologist.
• Blood pressure control, reduction of proteinuria and cholesterol reduction are all useful therapeutic manoeuvres in those with renal causes of NVH.
• All NVH patients should have long-term follow-up of their renal function and blood pressure (this can, and often should be, community-based).
• Renal function is measured using creatinine, and this is now routinely converted into an estimated glomerular filtration rate (eGFR) value quickly and easily.
• The most common imaging technique now used for the kidney is the renal ultrasound, which can detect size, shape, symmetry of kidneys and presence of tumour, stone or renal obstruction.

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Symptoms of chronic kidney disease (CKD) are often non-specific (Table 1.1). Clinical signs (of CKD, or of systemic diseases or syndromes) may be present and recognized early on in the natural history of kidney disease but, more often, both symptoms and signs are only present and recognized very late—sometimes too late to permit effective treatment in time to prepare for dialysis. However, the most commonly performed test of renal function—plasma creatinine—is typically performed with every hospital inpatient and as part of investigations or screening during many GP surgery or hospital clinic outpatient episodes.

Table 1.1 Signs and symptoms of chronic kidney disease

Symptoms	Signs
Tiredness	Pallor
Anorexia	Leuconychia
Nausea and vomiting	Peripheral oedema
Itching	Pleural effusion
Nocturia, frequency, oliguria	Pulmonary oedema
Haematuria	Raised blood pressure
Frothy urine
Loin pain

Unlike ‘angina’ or ‘chronic obstructive airways disease’, where a history can be revealing (e.g. walking distance or cough), there is little that is quantifiable about CKD severity without blood and/or urine testing.

This is why serendipitous discovery of kidney problems (haematuria, proteinuria, structural abnormalities on kidney imaging or loss of kidney function) is a common ‘presentation’. A full understanding of what these abnormalities mean and a clear guide to ‘what to do next’ are particularly needed in kidney medicine, and filling this gap is one of the aims of this book.

Correct use and interpretation of urine dipsticks and plasma creatinine values (by far the commonest tests used for screening and identification of kidney disease) is the main focus of this chapter. Renal imaging and renal biopsy will also be described briefly.

Urine Testing

Urinalysis is a basic test for the presence and severity of kidney disease. Testing urine during the menstrual period in women, and within 2–3 days of heavy strenuous exercise in both genders, should be avoided, to avoid contamination or artefacts. Fresh ‘mid-stream’ urine is best, again to reduce accidental contamination. Refrigeration of urine at temperatures from +2 to +8°C assists preservation. Specimens that have languished in an overstretched hospital laboratory specimen reception area, before eventually undergoing analysis, will rarely reveal all of the potential information that could have been gained.

Changes in urine colour are usually noticed by patients. Table 1.2 shows the main causes of different-coloured urine. Chemical parameters of the urine that can be detected using dipsticks include urine pH, haemoglobin, glucose, protein, leucocyte esterase, nitrites and ketones. Figure 1.1 shows the dipstick in its ‘dry’ state and an example of a positive test. Table 1.3 shows the main false negative and false positive results that can interfere with correct interpretation.

Table 1.2 The main causes of differently coloured urine

Pink–red–brown–black	Yellow–brown	Blue–green
Gross haematuria (e.g. bladder or renal tumour; IgA nephropathy)	Jaundice Drugs: chloroquine, nitrofurantoin	Drugs: triamterene
		Dyes: methylene blue
Haemoglobinuria (e.g. drug reaction)
Myoglobinuria (e.g. rhabdomyolysis)
Acute intermittent porphyria
Alkaptonuria
Drugs: phenytoin, rifampicin (red); metronidazole, methyldopa (darkening on standing)
Foods: beetroot, blackberries

Figure 1.1 Urine dipstick—the urine on the right is normal and the colours of all of the squares on the urine dipstick are normal/negative. The urine on the left is from someone with acute glomerulonephritis, looks pink-brown macroscopicall...