Appeal type: Inpatient Hospital
Decision: Unfavorable

 We decided that the Plan does not have to pay for inpatient hospital services provided on December 15, 2021, 
to December 22, 2021, at the Diagnosis Related Group (DRG) originally billed. 
 
You asked the Plan to pay for the inpatient hospital services at the DRG originally billed. You say that you 
disagree with the Plan's denial. The Plan denied your request. The Plan says the services are not payable as 
billed. 
 
The Plan must follow Medicare rules. Medicare rules say that providers must report services correctly. 
Providers must report inpatient hospital services with the appropriate DRG, which is based, in part, on the 
reported principal and secondary diagnosis codes.   
 
In this case, you billed the inpatient services provided with principal diagnosis code, N17.9, defined as acute 
kidney failure. We asked our physician reviewer to carefully review the case file and apply the relevant 
Medicare rules to determine if the Plan was correct in denying the request to pay for the inpatient hospital 
services at the DRG originally billed. Our reviewer says that the diagnosis billed are not supported. Our 
physician reviewer found the enrollee presented to the emergency department with weakness. The evaluation 
revealed a urinary tract infection and creatinine 2.0/ blood urea nitrogen (BUN) 74. The enrollee was treated 
with antibiotics and IV fluids and the enrollee's creatinine returned to baseline (1.5). The enrollee's condition 
stabilized and improved and the enrollee was discharged home December 22, 2021. 
 
Per Medscape Internal Medicine, Acute tubular necrosis (ATN) follows a well-defined three-part sequence of 
initiation, maintenance, and recovery. The initiation phase is characterized by an acute decrease in glomerular 
filtration rate (GFR) to very low levels, with a corresponding sudden increase in serum creatinine and BUN 
concentrations. The maintenance phase is characterized by a sustained severe reduction in GFR that persists for 
a variable length of time, most commonly one to two weeks. Because the filtration rate is so low during the 
maintenance phase, the creatinine and BUN levels continue to rise. 
 
The recovery phase, in which tubular function recovers, is characterized by an increase in urine volume (if 
oliguria was present during the maintenance phase) and by a gradual decrease in BUN and serum creatinine to 
their preinjury levels. The tubule cell damage and cell death that characterize ATN usually result from an acute 
ischemic or toxic event. Nephrotoxic mechanisms of ATN include direct drug toxicity, intrarenal 
vasoconstriction, and intratubular obstruction. Most of the pathophysiologic features of ischemic ATN are 
shared by the nephrotoxic forms. 
 
The history, physical examination, and laboratory findings, especially the renal ultrasonogram and the 
urinalysis, are particularly helpful in identifying the cause of ATN. Therapeutic mainstays are prevention, 
avoidance of further kidney damage, treatment of underlying conditions, and aggressive treatment of 
complications. 
 
The review has determined that the documentation did not support principal diagnosis code N17.9 (acute 
kidney failure). The enrollee had baseline chronic kidney disease and the enrollee's elevated creatinine on 
presentation returned to baseline with IV fluid therapy.  
 
We looked at this physician's review, the file, and Medicare rules. Based on this information, we decided the 
medical records do not substantiate the DRG as billed. Therefore, we decided that the Plan does not have to pay 
for inpatient hospital services provided on December 15, 2021, to December 22, 2021, at the Diagnosis Related 
Group (DRG) originally billed.