PITTSBURGH — Southwestern Pennsylvania’s second-largest medical provider will “show substantial operating losses” after an outside review found its accountants overstated the amount of money coming in.

West Penn Allegheny Health System announced Monday the adjustment to its balance sheet was approximately $73 million.

The losses relate “to current and prior fiscal years,” system spokesman Tom Chakurda said. He would not elaborate.

The problem was discovered when the hospital system reviewed its accounting practices with the help of an outside accounting firm.

“The review disclosed that West Penn Allegheny’s accounting methodology was overestimating the system’s net accounts receivable,” West Penn Allegheny said in a statement. “As a result, the system expects to show substantial operating losses.”

The hospital system has a $1.5 billion budget, Chakurda said. He declined further comment Monday.

“While this discovery is disappointing, it is essential information that allows us to build a plan for a sustainable future. ... What we have gained in this review of our finances is clarity,” West Penn Allegheny president and CEO Dr. Christopher Olivia said in a statement.

Olivia said the system has adopted an industry “best practice” accounting methodology to ensure the problem does not recur.

Olivia took over in March for CEO Jerry Fedele, who quit last summer. Kevin Smith had served as interim chief executive before stepping down from the board in June.

Other top officers have also left West Penn Allegheny recently.

Dawn Javersack quit this month after serving as vice president and chief financial officer. Another financial officer, David Samuel, left in March and former chief operating officer James Rosenberg left in May.