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Renal Failure, Chronic and Dialysis Complications: Differential Diagnoses & Workup

Author: Richard S Krause, MD, Senior Faculty, Department of Emergency Medicine, State University of New York at Buffalo School of Medicine
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Updated: Jun 9, 2009

Differential Diagnoses

Renal Failure, Acute

Workup

Laboratory Studies

Because of the primacy of the kidney in regulating metabolism, the concentrations of many chemical constituents of the body are abnormal in patients with chronic renal failure (CRF). The hematologic system is affected and thus the cellular components of the blood. Knowledge of the expected abnormalities and of the patient's baseline is necessary in evaluating patients with CRF. The following are the most important and frequently encountered abnormalities:

• Hyperkalemia is the most common clinically significant electrolyte abnormality in CRF.
  • It is often asymptomatic until potentially lethal dysrhythmias occur.
  • Hyperkalemia is uncommon when patients with end-stage renal disease (ESRD) are compliant with treatment and diet, unless an intercurrent illness such as acidosis or sepsis develops.
  • Serum potassium usually should be measured in patients with CRF/ESRD who present with a systemic illness or major injury.
  • History of hyperkalemia requiring treatment should lower the threshold for ordering a potassium level.
• BUN and serum creatinine are elevated chronically in patients with CRF and ESRD.
  • In patients who are not on dialysis, the degree of elevation is loosely reflective of the degree of renal impairment.
  • In patients with ESRD, the degree of elevation reflects the intensity and frequency of dialysis. Elevations of BUN and creatinine alone in patients with ESRD do not require emergency treatment.
  • BUN and creatinine elevations above baseline may be a sign of rejection in renal transplant patients and of deterioration in renal function in patients with predialysis CRF.
  • When such patients with residual renal function present with any suspected serious illness or urinary complaint, measure the BUN and creatinine and compare to baseline. Patients often are aware of their baseline BUN and creatinine.
• Baseline anion gap metabolic acidosis is typical in patients with CRF, who have a decreased ability to excrete acid. These patients are very prone to developing severe acidosis when under physiologic stress (eg, sepsis, myocardial infarction [MI], trauma).
  • Dialysis is necessary if the patient has severe acidosis.
  • Treat patients with significant chronic acidosis with oral alkalinizing agents to prevent bone loss.
  • Shortness of breath in patients with CRF may be due to respiratory compensation for acidosis.
• Anemia is invariable in patients with CRF. This is primarily due to loss of erythropoietin production. Comparison with baseline values often is useful for evaluation of anemia.
• Abnormal bleeding, primarily due to abnormal platelet function, is common on patients with CRF. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) usually are normal. When necessary, measurement of bleeding time is the best way to determine hemostatic competency.
• CAPD-associated peritonitis presents typically with diffuse abdominal pain. The diagnosis is confirmed by culture of effluent dialysate (ie, peritoneal fluid), which should be ordered prior to empiric treatment. Presumptive diagnosis is based on a peritoneal fluid WBC count of more than 100/mL or a positive Gram stain. The effluent is often cloudy when peritonitis is present, and this appearance accurately predicts elevated WBC counts. In patients without peritonitis, WBC counts of 0-50 with a mononuclear predominance are considered normal. Cell counts are usually much higher with predominant PMNs when peritonitis is present.
• Pancreatitis occurs with increased frequency in patients with ESRD. Since renal insufficiency may elevate amylase levels falsely, measurement of serum lipase is preferable, as this will lead to fewer false positive results.
• Total creatine phosphokinase (CPK) measurements may be elevated falsely in patients with renal failure. Tests for cardiac-specific markers, such as CPK-MB mass assays or cardiac troponins (I and T), may be more useful when MI is suspected. Asymptomatic patients with ESRD are more apt to have elevated levels of TnT than of TnI. The significance of these elevations is unclear but may be a marker for long-term cardiac risk. In patients with atypical symptoms, comparison with a baseline value may be very useful when it is available.⁴
• Infection should be suspected in patients who present with febrile illness. Patients are at increased risk of infection because of immunosuppressive effects of antirejection drugs (ie, transplant patients) or impaired immune function from uremia (ie, other patients with ESRD). Consider blood cultures when these patients present with febrile illnesses.

Imaging Studies

• Imaging studies in patients with CRF are ordered as indicated by the presenting complaint.
• Studies involving intravenous (IV) contrast may proceed in patients with ESRD who have no residual renal function.
• Contrast material given orally and or in retrograde urologic studies is not nephrotoxic and may be used in patients with CRF or ESRD.
  • Nephrotoxic effects of IV contrast must be considered in patients who are not yet on dialysis or who have received a transplant.
  • Consultation with a radiologist or nephrologist is advisable before giving IV contrast to such patients; consider alternatives to contrast.

Other Tests

• Electrocardiography (ECG) may be useful in diagnosis of suspected hyperkalemia.
  • Findings of severely peaked T waves are a relatively specific although not very sensitive test for hyperkalemia in the setting of CRF. Widening of the QRS complex indicates severe hyperkalemia and must be treated aggressively and rapidly.
  • Similar "hyperacute" T-waves may be seen early in acute MI.

Procedures

• Peripheral hemodialysis access sites may be used to draw blood or infuse medications and fluids in an emergency when no other access is available.
• A central venous access device may be used with the usual precautions.
• The following procedure may be used when hemodialysis access is used in an emergency:
  • Do not use a tourniquet.
  • Avoid puncturing the back wall of the vessel.
  • Carefully secure all IV catheters; infusions may need to be under pressure because of relatively high pressures at the access site.
  • Apply firm but nonocclusive pressure for 10-15 minutes after accessing a peripheral hemodialysis access site.
  • Document presence of a thrill before and after procedure.
• A patient with ESRD who has no residual urine output may have a lower urinary tract infection (a pus-filled bladder is known as pyocystis).
  • Consider bladder catheterization in patients with ESRD who present with fever or lower abdominal pain.
  • If purulent material is obtained, send it for culture.

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