Renal impairment

Renal impairment is a common complication in myeloma. At diagnosis, up to half of patients present with some degree of renal dysfunction. It can also evolve over time.

There are many causes of renal impairment that involve different mechanisms. In myeloma, the major causes of renal impairment are:

• Cast nephropathy (myeloma kidney disease) – occurs as a result of the precipitation of free light chains in the renal tubules
• Hypercalcemia – where blood calcium concentrations are >2.6mmol/L due to bone breakdown as a consequence of myeloma bone disease
• Urinary tract infection and sepsis
• Exposure to nephrotoxic drugs such as bisphosphonates, NSAIDs, antibiotics and contrast media
• Dehydration
• Related disorders such as AL amyloidosis

Renal impairment due to bisphosphonate treatment is most likely when the recommended dose or rate of infusion is exceeded. Many drugs cause renal impairment and the full list is available from the British National Forum (BNF) at www.bnf.org.

Co-morbidities such as diabetes, hypertension, prostatic obstruction and congestive heart failure can also contribute to renal impairment.

The clinical consequences of renal impairment include:

• Metabolic acidosis
• Uraemia
• Anaemia
• Fluid and electrolyte imbalance
• Cardiovascular, gastrointestinal and neurological complications
• Renal failure

A diagnosis of renal impairment can be difficult because symptoms are often vague and the impact not apparent until it is quite advanced. Symptoms vary and can affect a number of organs and tissues as described in Table 4.

Table 4: Symptoms associated with renal impairment

Provided patients are diagnosed early, rapid intervention in most cases can successfully reverse renal impairment. However, if left untreated, renal damage may become irreversible and potentially life-threatening. After infection, renal failure is the second most common cause of death in myeloma patients.

Nurses should be vigilant for the signs and symptoms of renal impairment. Nurses play a key role in the assessment, monitoring and management of this potentially serious complication and help provide timely intervention and support to optimise patient outcomes.

Watch the following animation about myeloma kidney disease:

Assessment of renal impairment

The most common laboratory findings which suggest renal impairment in myeloma patients are asymptomatic proteinuria and/or elevated serum creatinine levels.

The normal serum creatinine range is 70 – 120µmol/L. Impaired renal function is defined as a serum creatinine level > 132µmol/l whereas renal failure is defined as a serum creatinine level > 177µmol/l.

For a more accurate assessment of renal function, the estimated glomerular filtration rate (eGFR) or creatinine clearance from a 24 hour urine collection should be calculated. To obtain an accurate GFR e.g. prior to high dose therapy/stem cell transplant, EDTA testing should be performed. Assessment of other blood and/or urinary parameters also provides a good indication of renal function. These include measurement of: albumin, urea, urate, electrolytes, proteinuria, CRP and parathyroid hormone.

Treatment for renal impairment

The most effective way of treating myeloma-related renal impairment is to reduce the light chain load being delivered to the kidneys. This is best done by treating the myeloma itself.
Oral high-dose dexamethasone is often started first and, in the majority of patients, other supportive approaches may be necessary before anti-myeloma treatments can be given (see below).

As some of the anti-myeloma treatments are also potentially nephrotoxic, doses may need to be adjusted depending on the extent of renal impairment or alternative treatments used.

Light chain load can also be reduced by physically removing them from the plasma by a process known as plasmapheresis, although the success of the technique is varied.

Prevention and management of renal impairment

Patient education is paramount in preventing and managing renal impairment. Nurses play a key role in informing all myeloma patients of the risk of impaired renal function, how to recognise any signs or symptoms and to know how, when and to whom they should report to.

• Ensuring patients understand the need to maintain a high fluid intake throughout the course of their myeloma is key to the management of renal impairment. Advise patients to drink at least 2 litres (3-4 pints) a day. This does not have to be exclusively water but can be made up of beverages such as fruit juice, diluted squash, tea etc

Some patients find this challenging to achieve and require encouragement to so. It is important they understand why they must let their team know if they are unable to maintain this amount, or if they are losing fluids because of episodes of diarrhoea or vomiting. Nurses should also advise on avoiding potentially nephrotoxic over-the-counter painkillers, such as aspirin and ibuprofen.

Prompt intervention is vital to correct early renal impairment and prevent long-term damage. Medical management strategies focus on correcting the reversible causes of renal impairment and include one or more of the following:

• Rehydrating with at least 2 litres of normal saline daily (unless otherwise contraindicated e.g. heart failure or oliguric renal failure)
• Correcting hypercalcaemia with modified doses of bisphosphonate
• Discontinuing nephrotoxic drugs such as NSAIDs and aminoglycoside antibiotics
• Rapid treatment of infections
• Treating chronic anaemia with blood transfusions and/or erythropoietin-stimulating agents

In most cases, renal function will start to improve within 48 hours of an intervention but if not, advice should be sought from the renal team. Renal dialysis (haemodialysis or peritoneal dialysis) may be necessary for those with severe renal impairment.

All patients on bisphosphonates should have their renal function monitored regularly. Bisphosphonate treatment may need to be stopped until the cause of renal impairment is found. Otherwise, dose modification may be required as shown in Table 5. Although not routinely funded for use in myeloma, in some cases where patients with renal impairment are not able to receive bisphosphonates, the use of denosumab may be granted.

Table 5: Manufacturers’ guidance for dose adjustment of bisphosphonates for renal impairment

Patients and their families should also be advised of the benefits of lifestyle changes in reducing the risk of or in improving renal impairment. Where appropriate, patients should be encouraged to stop smoking, exercise, consume a healthy low-salt diet and manage their weight.

Effective treatment and management can, in most cases, reverse renal damage and in this regard, nurses play a crucial role in assessing and monitoring the signs and symptoms of renal impairment and keeping patients and their families informed and educated about the importance of maintaining renal health. Read more in our Myeloma Nurse Guide: Myeloma Kidney Disease.

Watch the following clip of a myeloma patient talking about living with renal impairment:

Further reading

NICE (National Institute for Health and Care Excellence) Acute kidney injury: prevention, detection and management (NG148)

NICE (National Institute for Health and Care Excellence) Chronic kidney disease: assessment and management (NG203)