Acute Renal/Kidney Failure/Injury vs Dehydration as a Principal Diagnosis

Patients being admitted for acute renal failure due to dehydration have been happening for many, many years now. Typically what happens is a patient gets dehydrated for one reason or another. Once dehydration sets in, it can quickly start to affect many body organs. One of these is the kidneys. This can lead to acute renal/kidney failure/injury.

Dehydration

Dehydration results from excessive water loss from body tissues. Etiologies include but are not limited to extensive vomiting, diarrhea, gastroenteritis, renal or adrenal disease, diabetes mellitus, diuretic therapy, or having an ileostomy or colostomy. Symptoms include diminished skin turgor or a “tenting” of the skin, dry oral mucosa and skin, a shrunken tongue, tachycardia, low central venous pressure, postural hypotension, and in severe cases, disorientation and shock. Lab tests that help diagnose dehydration are elevated BUN, elevated Hgb and hematocrit, elevated potassium and decreased sodium. Treatment is IV fluids and sodium, usually at a high IV rates 125cc/hr to 250cc/hr. However, the size of the patient will dictate how much fluid and what rate it is infused. So there is no hard and fast rule. Sometimes fluid boluses are given right away to address significant dehydration.

Dehydration is coded to E86.0, Dehydration, and results in DRGs:

641, Misc disorders of nutrition, metabolism, fluids/electrolytes w/o MCC, Weight 0.7702
640, Misc disorders of nutrition, metabolism, fluids/electrolytes w MCC, Weight 1.2653

Acute Kidney Failure/Injury

Acute renal/kidney failure or injury is a sudden, severe onset of inadequate kidney function. There are many causes of acute renal/kidney failure/injury, however, when due to dehydration, it is because there is decreased renal blood flow from lower blood pressure because of the dehydration. This starts causing functioning problems with the kidney. Symptoms include oliguria, edema resulting from salt and water overload, nausea and vomiting, lethargy from the toxic effects of the waste products building up, hydronephrosis and at times metabolic acidosis. BUN and creatinine will be significantly elevated. There are several types of criteria for acute kidney failure/injury and some hospitals compile their own.

Some well known clinical criteria for validating this diagnosis are:

• RIFLE (Risk of renal dysfunction, Injury to kidney, Failure or Loss of kidney function,
  and End-stage kidney disease)
• AKIN (Acute Kidney Injury Network stage)
• KDIGO (Kidney Disease: Improving Global Outcomes group)

Treatment involves treating the underlying cause, and if due to dehydration, that means treating the dehydration with fluids. Renal function (BUN, creatinine) would be followed and monitored along with fluid intake. Acute kidney failure/injury can be life threatening if severe as the kidneys can shut down.

Acute renal failure/injury is coded N17.9, acute kidney failure, unspecified and if PDX leads to these DRGs:

684, Renal failure w/o CC/MCC Weight 0.6048
683, Renal failure w CC Weight 0.8949
682, Renal failure w MCC Weight 1.4866

Past advice is now superseded

There is a very old Coding Clinic, Third Quarter 2002, pages 21-22 with two questions involving acute renal/kidney failure due to dehydration. In both questions, AHA advised to report the acute renal/kidney failure/injury code as the principal diagnosis. Coders have been following that advice since it was published. Until Coding Clinic First Quarter, 2019 page 12.

In Coding Clinic First Quarter 2019 page 12, AHA is now stating that there is no rule that acute renal/kidney failure/injury should always be sequenced first in these situations. They now are stating the sequencing of either dehydration or acute renal/kidney failure/injury should be based on the reason for admission. If it cannot be determined, or is not clearly documented, the physician should be queried.

What is a coder to do?

This is now a dilemma. Best practice is for the coder to look at both conditions documented clinically and carefully, remembering that every patient is different. Review the admission order to see if the physician is indicating the exact reason for admission. Look at the ED record and observation record to see what was treated and resolved before true inpatient admission. Look at the clinical indicators to see if both of the diagnoses are solidly supported by the documentation. Is one condition documented more acutely than the other? For example, in looking at the serum creatinine, was the increase only 25% and creatinine at 1.9 which is not twice the patient’s baseline? Was BUN only slightly elevated from the patient’s baseline? Were IV fluid boluses immediately given and IV set at 175 cc/hr? This may indicate that the dehydration was more of an acute reason for admission than acute renal failure/injury. Then there is the question of true acute renal/kidney failure/injury clinical validation in the case.

CDI professionals will also have to be sure physicians are documenting clinical indicators that would support acute renal/kidney failure/injury rather than only kidney insufficiency, which is coded differently and affects DRG assignment. Also, medications can sometimes affect the BUN and creatinine and it may not be a true indication of acute renal/kidney failure/injury. The coder should not be shy about escalating a case to CDI or a physician adviser if either diagnosis does not seem to be clinically validated, as this is part of a coder’s responsibility.

As can be seen in the DRGs above, choosing one of these diagnoses over the other as PDX can impact reimbursement. Having an MCC code on the record can also change up the DRG assigned and reimbursement. And of course surgical procedures can further change the DRG. It will be critically important that coders know the clinical indicators that validate these diagnoses, treatments rendered, and also remember that every patient is different. There is not one “across the board” answer as to what diagnosis is PDX for every patient who is admitted with acute renal/kidney failure/injury and dehydration.

References
Coding Clinic, First Quarter, 2019, page 12
sciencedirect.com/science/article/pii/S0929664617304035
kdigo.org/wp-content/uploads/2017/04/KDIGO-AKI-GL-for-JSN_wm.pdf