Renal failure after cardiac surgery

A 52 year old non-smoking black man presented with a two week history of dysuria, malaise, fever, and rigors. In the past he had had recurrent urinary tract infections requiring antibiotic treatment.

On clinical examination he had a temperature of 38.9°C, his pulse rate was 70 beats/min, and blood pressure was 125/70 mm Hg. A pansystolic murmur was auscultated, which was loudest at the apex beat and radiated to the left axilla. Urine dipstick was positive for protein and blood. Laboratory investigations showed a haemoglobin concentration of 9.7 g/dl (normocytic), white cell count of 12.2 ¥ 109/l (neutrophil count 8.8 ¥ 109/l), C reactive protein of 106 mg/l, erythrocyte sedimentation rate of 130 mm in the first hour, raised corrected calcium (2.73 mmol/l), and a total protein count of 113 g/l. Renal (urea 6.7 mmol/l, creatine 97 µmol/l, estimated glomerular filtration rate 91 ml/min/1.73 m2) and liver function tests were normal. An electrocardiogram showed normal sinus rhythm.

Fig 1 The results of an investigation

Transthoracic echocardiography confirmed a large bulbous mass on the posterior mitral valve leaflet. He was treated for infective endocarditis with intravenous benzylpenicillin and gentamicin, but his cardiac function deteriorated. Two weeks after admission he required a mitral valve repair. No organisms were isolated from the urine, blood, or excised mass; however, intravenous antibiotics were continued empirically.

After surgery his renal function gradually deteriorated. The benzylpenicillin and gentamicin were stopped, and he started taking a low dose of cefatrioxone. On the 20th day after the operation, his serum creatinine peaked at 323 mmol/l (glomerular filtration rate decreased to 29 ml/min), despite adequate fluid balance and a normally functioning mitral valve. An ultrasound scan of his renal tract was normal.

Questions

(1) What are the possible causes of the renal failure?

(2) What investigation is shown in fig 1?

(3) What further investigations would confirm the diagnosis of multiple myeloma?

Answers

(1) The most likely cause of the renal failure was acute tubular necrosis, secondary to ischaemia, sepsis, or gentamicin. Infection, anaemia, hypercalcaemia, raised erythrocyte sedimentation rate, and a high total protein count suggest multiple myeloma, which is another cause of acute tubular necrosis. The man had a background history of urinary tract infections, but ultrasonography of the renal tract did not show any renal scarring.

(2) Figure 1 shows a serum protein electrophoresis strip, with a monoclonal M band. In this case, the immunoglobulin was kappa-type IgG.

(3) The diagnosis of multiple myeloma can be confirmed by showing plasma cell infiltration on bone marrow aspirate or trephine biopsy (fig 2), osteolytic bone lesions on skeletal survey, and Bence Jones protein in the urine.

Fig 2 Trephine biopsy of the bone marrow

Discussion

Multiple myeloma is a neoplastic clonal proliferation of bone marrow plasma cells capable of producing abnormal immunoglobulins which are IgG or IgA in most cases. The immunoglobulin maybe associated with excretion of light chains in the urine (kappa or lambda). These excess light chains are known as Bence Jones protein. The neoplastic clone of cells induces excess osteolytic activity, which results in osteolytic lesions and hypercalcaemia. Progressive marrow infiltration results in anaemia, bleeding, and infections. Renal failure is multifactorial: deposition of light chains in the tubules, hypercalcaemia, hyperuricaemia, and amyloid deposition in the kidneys.

This case illustrates the difficulty and importance of early diagnosis of multiple myeloma as a cause for infective endocarditis.¹ Cardiac surgery on cardiopulmonary bypass alone is associated with postoperative renal dysfunction, and as many as 4% of patients with normal preoperative renal function develop acute renal failure.² Patients with multiple myeloma are at increased risk of acute renal failure. This should be anticipated preoperatively so that anaesthesia, surgery, and postoperative care can be tailored specifically to the disease.³ Early and aggressive use of haemofiltration is associated with better than expected survival in severe acute renal failure after cardiac surgery.⁴

Cardiac surgery in patients with multiple myeloma carries an increased morbidity, and should be carefully considered.⁵

Competing interests: None declared

Christiansen S, Schmid C, Loher A, Scheld HH. Impact of malignant haematological disorders on cardiac surgery. Cardiovasc Surg 2000;8: 149-52.