A urine bilirubin level of one (+) in routine urine tests suggests the possible presence of hepatocellular jaundice, which requires further examination of liver function, liver virology measurements and ultrasound of the liver to further rule out. When hepatocellular jaundice is present, elevated bilirubin levels in the blood can occur, with some bilirubin excreted in the urine and some bilirubin excreted from the intestine, and those excreted from the intestine can be converted to urobilinogen. Most of the bilirubin is excreted in the feces as fecal bilirubin, and some of the urobilinogen is reabsorbed into the liver through the portal vein, where it is combined again to form bilirubin and excreted into the intestine. However, a small amount of urobilinogen passes through the glomerulus or is filtered out through the renal tubules to form urobilinogen, which can increase urobilinogen levels. Urobilinogen also becomes urobilin when it comes into contact with air, and a routine urine test may be accompanied by a slightly higher level of bilirubin in the urine.