, Mark Thomas1 and David Milford2
(1)
Department of Renal Medicine, Birmingham Heartlands Hospital, Birmingham, UK
(2)
Birmingham Children’s Hospital, Birmingham, UK
Abstract
In this chapter we explain:
Risk assessment when considering a kidney biopsy
When a kidney biopsy is useful in someone with diabetes
No guidelines or consensus statements have been issued by specialist organisations to help clinicians decide when to perform a kidney biopsy . Therefore the following comments are our personal views, inevitably coloured by our clinical experiences.
‘Primum Non Nocere’ – First, Do No Harm
Most nephrologists know of patients who have come to serious harm as a result of a kidney biopsy. Even with ultrasound guidance, it is not possible to guide the needle to avoid blood vessels (see Fig. 16.1). Hence, every kidney biopsy causes bleeding; the issue is how much. Published reports state that about 1 in every 100 patients requires a blood transfusion. Unpublished results are likely to be higher. Fatality is much rarer but is a genuine risk that must be considered [1].
Kidney histology is fascinating and beautiful. However, curiosity about what will be found is, on its own, insufficient justification to perform a biopsy. Remember the old saying: ‘Curiosity killed the cat’. If you cannot answer the question: “How will the result of this biopsy affect the treatment plan and the likely outcome for the patient?” you should reconsider whether to seek the patient’s consent.
Although histology may sometimes provide a more precise prognosis, proteinuria and the trend in eGFR are often adequate guides to the patient’s future (see Sect. “The clinical significance of haematuria” in page 136). Using the results of the biopsy primarily for academic purposes requires the patient to give explicit consent, as they would for a research study.
Conventional inclusion criteria for considering a biopsy are based upon the likelihood of finding a treatable disease [2]. They include:
Proteinuria more than 1 g per day (PCR >100 mg/mmol, >1000 mg/g)
eGFR declining over weeks or months, with or without haematuria and proteinuria
Systemic illness with evidence of kidney involvement where a tissue diagnosis is needed
Exclusion criteria are based upon the likelihood of finding irreversible damage. They include:
Reduced kidney size with thin cortical width
eGFR declining over years
The risk of bleeding is greater in patients who have:
high serum urea
anaemia
low platelets or abnormal clotting
anticoagulant or antiplatelet therapy, e.g. clopidogrel
Is It Diabetic Nephropathy ?
The ‘to biopsy or not to biopsy’ dilemma often arises in people with diabetes. As diabetes is so common, it is possible that the patient has an unrelated kidney disease.
First, view the kidneys with an ultrasound scan. Diabetic nephropathy does not affect the ultrasound appearances, other than sometimes by increasing the echogenicity of the cortex so that the differentiation between the cortex and medulla is reduced.
If the ultrasound scan is normal, the following questions are helpful:
1.
How long has the patient been diabetic?
Nephropathy usually only develops once the patient has been diabetic for over 10 years. However, it can sometimes be difficult to estimate exactly how long diabetes has been present as type 2 diabetes can remain asymptomatic for a number of years. The likelihood of nephropathy is greater if there has been a long period of poor glucose control [3].
2.
Does the patient have type 1 or type 2 diabetes?
A renal biopsy is much less likely to reveal pathology other than diabetic nephropathy in someone with type 1 rather than type 2 diabetes.
3.
Has there been a change in the rate of decline in GFR?
A typical rate of decline in GFR in someone with diabetic nephropathy is 3 ml/min/1.73 m2/year [4]. However, in patients with poorly controlled blood pressure or a long history of poor glucose control the decline can be faster than 10 ml/min/1.73 m2/year.
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