From the Guidelines
Assessing renal function in a patient with paraplegia requires direct measurement of glomerular filtration rate (GFR) using clearance methods, such as urinary clearance of 125I-iothalamate, due to the potential for inaccurate estimates using serum creatinine concentration alone 1. When evaluating renal function in paraplegic patients, it is essential to consider the limitations of serum creatinine as a sole indicator of kidney function.
- Serum creatinine concentration can be affected by factors such as creatinine secretion and generation, and extrarenal excretion, leading to a wide range of normal values 1.
- In patients with paraplegia, decreased muscle mass can result in falsely low creatinine levels, making it challenging to accurately estimate GFR using prediction equations alone.
- Clinical conditions like paraplegia or quadriplegia require direct measurement of GFR using clearance methods, as stated in the national kidney foundation practice guidelines for chronic kidney disease 1. Regular monitoring of renal function should include:
- Direct measurement of GFR using clearance methods, such as urinary clearance of 125I-iothalamate, to accurately assess kidney function 1.
- Urine samples collected via clean intermittent catheterization, if the patient has neurogenic bladder, to monitor for urinary tract infections and assess kidney function.
- Regular ultrasounds to evaluate kidney structure and detect potential complications like hydronephrosis or stones.
- Comprehensive metabolic panels to monitor electrolyte levels, fluid status, and kidney function, with more frequent monitoring if abnormalities are detected.
From the Research
Assessing Renal Function in Paraplegic Patients
To assess renal function in a patient with paraplegia, several factors need to be considered due to the unique physiological changes that occur in these patients. The following points highlight key considerations:
- Creatinine Clearance: Nomograms commonly used to evaluate endogenous creatinine clearance may not be accurate for paralyzed patients, as they tend to overestimate creatinine clearance 2. This can lead to incorrect dosing of certain medications, such as aminoglycosides.
- Serum Creatinine: Serum creatinine levels may be within normal limits or only minimally elevated in patients with spinal cord injury, despite significant reductions in creatinine clearance 3. This suggests that serum creatinine is not a reliable indicator of renal function in these patients.
- Urinary Creatinine Excretion: Urinary creatinine excretion is lower in patients with spinal cord injury compared to able-bodied individuals 3. This decrease cannot be fully explained by differences in age, sex, or body weight.
- Equations for Estimating Creatinine Clearance: Specific equations, such as Ccr (mL/min) = 45/Scr (mg/dL), have been proposed to more accurately estimate creatinine clearance in patients with spinal cord injury 3.
- Clinical Considerations: Incomplete bladder emptying due to infravesical outflow obstruction is a main cause of urinary tract infections in paraplegic patients 4. Rehabilitation and management of paraplegia require an interdisciplinary approach, including attention to urinary and bowel continence, mobility, and lifelong follow-up 5.
- Diagnostic Challenges: Clinical signs of urinary tract infection correlate poorly with urine colony-forming units (cfu) and white blood cell (WBC) levels in spinal cord injury patients, making diagnosis challenging 6.
Key Factors for Accurate Assessment
- Use of specific equations to estimate creatinine clearance, such as those taking into account the patient's spinal cord injury 2, 3.
- Consideration of the unique physiological changes in paraplegic patients, including lower urinary creatinine excretion 3.
- Awareness of the potential for overestimation of renal function using standard nomograms 2.
- Comprehensive management and rehabilitation strategies to address the complex needs of paraplegic patients, including prevention and treatment of urinary tract infections 4, 5.