When a left subcostal mass is palpated during an abdominal examination, many will assume it is a spleen while, in fact, many structures could be the source, including the left lobe of the liver, the colon, the chest wall, etc. However, the first important differential diagnosis to consider must be the kidney, which is the focus of this clinical pearl.

SPLEEN VS KIDNEY

-Mnemonic: There is a real bad kid named Ben, and he pushed another kid named Fin. When asked about it, all of a sudden, “Ben Can Not Remember Pushing Fin!!” I think he is lying but anyways:

1- Ben: Ballotability 🎈: A SPLEEN is NOT ballotable, except in cases of severe ascites where it becomes suspended in fluid just like a fetus, and a KIDNEY is ballotable because of its retroperitoneal position.

2- Can: Can’t feel above it (no emoji for this one lol): Which means there is no space between the SPLEEN (above it) and the costal margin to be felt, because the spleen sits high up in the abdomen and is tucked in deep, spanning the 9th, 10th, and 11th ribs posteriorly, while the same space is present for the KIDNEY because, well, it’s in a lower part of the abdomen.

3- Not: Notch 🔻: The SPLEEN is notched—has a notch that can be palpable—and the KIDNEY is not.

4- Remember: Respiration movement 🏃: The SPLEEN moves inferomedially, towards the right iliac fossa, with respiration, guided by the splenorenal ligament, while the KIDNEY moves only inferiorly.

5- Pushing: Percussion note 🥁: Percussion over a SPLEEN yields a DULL note, and over a KIDNEY yields a TYMPANIC one, because of the band of colonic resonance.

6- Fin: Friction Rub 🩺: This is an uncommon one, but a friction rub can occasionally be heard over a SPLEEN, say because of a splenic infarction, while it can’t be heard over a KIDNEY, again, because of its retroperitoneal position.