How many of you have spoken with patients who complain of mid-back pain and tell you that their kidneys hurt? While dull, aching pain in the mid-lower back is more likely to be associated with musculoskeletal etiologies, kidney-related pain typically presents as sharp, colicky flank pain. Kidney pain usually results from distension of the well-innervated renal capsule due to subcapsular swelling. Specific causes include:
1. Nephrolithiasis. A kidney stone lodged in a ureter or in the kidney parenchyma can obstruct the flow of urine and cause subcapsular swelling and hence, pain. Pain is classically severe, localized to the flank with occasional radiation to the groin, colicky in nature, and may be associated with nausea and vomiting.
2. Pyelonephritis/UTI. Infection and inflammation of the renal parenchyma can also lead to swelling and distension of the renal capsule.
3. Renal masses. This can be in the form of cysts (i.e. polycystic kidney disease) or tumors such as renal cell carcinoma or angiomyolipomas, either of which may distend the renal capsule and cause pain.
4. Renal hemorrhage (intraparenchymal bleeding due to injury or trauma).
6. Renal infarction. A rare cause of kidney pain, this can be due to a thromboembolic event or an in situ thrombosis of the renal artery or its branches. It typically presents with sudden onset, acute flank pain or abdominal discomfort, usually associated with nausea and vomiting. Fever can sometimes be seen as well.
7. Renal vein thrombosis. Can be more insidious or present acutely like renal infarction with sudden onset flank pain.