Assessment For Kidney Transplantion
Although renal transplantation improves both quality of life and survival, it involves a significant investment of health resources and the use of an organ with a limited supply. It is therefore of utmost importance that the potential transplant recipient is carefully assessed, both to avoid unnecessary exposure to the risks of a general anaesthetic and to ensure appropriate use of a precious resource. To this end, every potential transplant recipient is assessed by taking a careful history, performing a thorough examination and undertaking a number of investigations.
The transplant work-up must answer five questions.
1 Does the patient have any medical problems which put them at risk of operative morbidity/mortality? Patients with CKD are at increased risk of coronary, cerebral and peripheral vascular disease, and should be assessed for a past or current history of cardiac problems (e.g. angina, myocardial infarction, rheumatic fever), strokes or peripheral vascular disease (claudication/amputation). Risk factors assessed include family history, smoking history and a history of diabetes mellitus or hypercholesterolaemia. Smoking is also associated with the development of chronic obstructive pulmonary disease (COPD). A good screening question to assess general cardiorespiratory fitness is to ask how far the patient can walk; a good test is to make them walk.
Dialysis patients are frequently oligo-anuric and often struggle to restrict their fluid intake. This leads to chronic volume overload and hypertension, resulting in left ventricular hypertrophy (LVH) or dysfunction. Patient who require 3–4 litres of fluid to be removed at each dialysis session frequently develop such cardiac problems.
CKD is also associated with tertiary hyperparathyroidism and hypercalcaemia, which increases the risk of vascular and valvular calcification, particularly the aortic valve.
Examination should pay particular attention to cardiovascular signs: pulse rhythm and volume, signs of volume overload (ele- vated jugular venous pressure [JVP], peripheral and pulmonary oedema), signs of LVH (hyperdynamic apex beat) or LV dilatation (displaced apex beat) and signs of valvular heart disease (particularly the ejection systolic murmur of calcific aortic stenosis). The chest should be assessed for signs of COPD (hyperinflation, reduced expansion, wheeze) or for pleural effusions which may occur in patients on peritoneal dialysis.
Cardiorespiratory investigations include an electrocardiogram (ECG), a chest radiograph, a cardiac stress test (an exercise tolerance test or an isotope perfusion study) and an echocardiogram (to assess LV function). If these are abnormal, then the patient may need further cardiological assessment, including coronary angiography.
2. Does the patient have any conditions that make them technically difficult to transplant?
There are four basic technical requirements for implantation of a kidney.
· An artery (usually the external iliac artery), to which the trans- plant renal artery will be anastomosed. Severe vascular disease can make the arterial anastomosis difficult, therefore all of the patient’s lower limb pulses should be carefully assessed during examination, including auscultation of the femoral arteries and aortic bifurca- tion for bruits, as a surrogate for iliac artery disease. Duplex imaging is indicated if any abnormality is detected or suspected.
· A vein (usually the external iliac vein), to which the transplant renal vein will be anastomosed. A history of venous thromboem- bolic disease, particularly clots in the lower limb veins, should be sought; a transplant should not be placed above a limb where a thrombosis has occurred previously. Patients on chronic haemo- dialysis may have had numerous lines inserted into their femoral veins, which can lead to stenosis and thrombosis. Look for col- laterals, cutaneous signs of venous hypertension and oedema, which may be associated with venous compromise. Duplex imaging or percutaneous venography may be required.
· A bladder, to which the transplant ureter will be anastomosed. A history of urological problems, including congenital bladder malformations or reflux, is of relevance. If these issues are not resolved prior to transplantation, then they may recur and damage the transplanted kidney. Patients who have had ESRF for a number of years often have negligible urine output and a small, shrunken bladder, which is difficult to find intra-operatively and will only hold small volumes of urine post transplant. Some patients need a neobladder fashioned from a segment of their ileum (a urostomy).
· Space for the kidney. Some patients with polycystic kidney disease have grossly enlarged native kidneys that extend into the lower abdomen and may require removal prior to transplantation. In addition, patients with an elevated body mass index (BMI) may be technically difficult to transplant, due to lack of space for the graft and reduced ease of access to the vessels. Therefore, most centres will not list patients for transplantation unless the BMI is <35 kg/m2.
3. Is the patient at increased risk of the immunological complications of transplantation?
The immune system remains a significant barrier to transplantation in patients with pre-formed antibodies to non-self human leucocyte antigens (HLA). This usually occurs as a result of a sensitising event, for example blood transfusion, pregnancy (particularly by multiple partners), or previous renal transplants or other allografts (e.g. skin grafts). The frequency of such events should be ascertained.
4. Is the patient at increased risk of immunosuppression-associated complications?
Patients with ESRF secondary to a primary or secondary glomerulonephritis (e.g. IgA, vasculitis or lupus) have frequently been treated with immunosuppressants. This includes the use of toxic agents, such as cyclophosphamide, or biological agents, including alemtuzumab or rituximab. Heavy immunosuppression should be avoided in such patients post-transplant, particularly the use of lymphocyte-depleting agents such as anti-thymocyte globulin (ATG), which may place them at high risk of infectious complications.
Immunosuppression also increases the risk of developing a de novo cancer (particularly oncovirus-associated malignancies), and enhances the progression of existing cancers. Thus, most centres would agree that patients with a history of malignancy must be cancer-free for at least 5 years prior to transplantation.
5. Is the patient at risk of recurrent disease in their transplant?
Some pathologies that cause CKD can recur in the transplant and reduce its long-term function and survival. A number of glomerulonephritides can affect the graft (e.g. IgA nephropathy and focal segmental glomerulosclerosis [FSGS]). In the case of FSGS, the patient may develop recurrent disease immediately post transplant (usually evidenced by heavy proteinuria). This is sometimes amenable to treatment with plasma exchange, therefore it is important to recognise this risk and carefully monitor the patient post transplant. If a patient has developed rapidly progressive, recurrent disease in a transplant kidney, then this is a relative contraindication to re-transplantation.