title: The diagnoses and co-morbidity encountered in the hospital practice of acute internal medicine.
abstract: BACKGROUND
  The exact medical conditions that every internist needs to know how to diagnose and treat have seldom been explicitly stated. This paper reports an analysis of the conditions, as identified by ICD9 coding, cared for by general internists working in a representative Irish hospital.
  
  
  METHODS
  In this observational study covering the period from February 17, 2000 to January 29, 2004, the ICD9 codes and mortality of 9214 consecutive patients admitted as acute medical emergencies were examined.
  
  
  RESULTS
  The mean number of ICD9 codes per patient was 4.0+/-1.8 (median 4.0 codes); 935 patients (10.1%) had one ICD9 code and 2972 (32.3%) had six ICD9 codes recorded at the time of discharge. As the number of ICD9 codes recorded increased, so did patient age, 30-day mortality and length of hospital stay. Thirty-four conditions were found to be associated with a statistically significant increased risk of 30-day mortality, and eight with a significantly reduced risk. Of the remaining conditions (i.e. those with neither an increased nor reduced risk of mortality), 32 were observed in 1% or more of all patients.
  
  
  CONCLUSIONS
  Nearly all of the clinical presentations encountered are encompassed within an average of four combinations of 74 conditions, 34 of which are associated with an increased risk of death.
authors.affiliation: Consultant Physician, Nenagh Hospital, Nenagh, Co. Tipperary, Ireland.
authors.forename: John
authors.initials: J
authors.lastname: Kellett
authors.forename: Breda
authors.initials: B
authors.lastname: Deane