Renal concentration capacity in adult patients with urinary tract infections

The maximal urine concentration capacity was studied in patients with acute pyelonephritis and in patients with clinically diagnosed acute cystitis. In the former group renal concentration ability was reduced in 16 of 22 patients and improved in all but two patients. Among patients with symptoms of acute cystitis 6 of 22 had a concentration capacity below 2 SD of normal values. Several of these patients had raised acute phase proteins and increased their urine osmolality at follow-up indicating that cases of acute pyelonephritis could have been included. It is concluded that the wide overlap between the groups makes the maximal urinary concentration capacity a method of limited value for level diagnosis in acute UTI infection. The test should be reserved for follow-up to reveal permanent renal damage.