Pneumonia in hemodialysis patients: a challenging diagnosis in the emergency room.

Background: Diagnosing pneumonia in hemodialysis patients is challenging. We hypothesized that pulmonary edema, which occurs commonly in hemodialysis patients, may frequently be misdiagnosed as pneumonia.

Methods: We retrospectively reviewed the records of 105 hemodialysis patients admitted with the diagnosis of pneumonia. Two experienced radiologists masked to the clinical course and subsequent imaging, independently interpreted the admission chest radiographs. In 68 of the patients, 2 internists independently reviewed the hospitalization records to diagnose pneumonia and pulmonary edema. The level of agreement among the radiologists was assessed using the kappa test. Using the clinical diagnoses, chest radiograph attributes were calculated. Logistic regression was performed to identify clinical and laboratory markers associated with pneumonia and pulmonary edema.

Results: The radiologist showed slight agreement on pneumonia (κ = 0.32) and pulmonary edema (κ = 0.28). Using clinical consensus, pneumonia was diagnosed in only 21% (14/68) of patients. Chest radiograph attributes for diagnosing pneumonia included: sensitivity 50%, specificity 58%, positive predictive value 25% and negative predictive value 81%. Pneumonia was associated with presenting temperature (odds ratio [OR] = 
2.01; 95% CI, 1.03-3.93). Pulmonary edema was associated with shortness of breath (SOB) at admission 
(OR = 4.83; 95% CI, 1.25-18.6), presenting temperature (OR = 0.44; 95% CI, 0.21-0.92) and volume removed during hemodialysis (OR = 1.96; 95% CI, 1.16-3.31).

Conclusions: The admission chest radiograph has significant limitations when used to diagnose pneumonia in hemodialysis patients. A high presenting temperature supports the diagnosis of pneumonia, while a low presenting temperature, SOB and large volume ultrafiltration favor the diagnosis of pulmonary edema.