Is it uncommon to have a kidney stone in the parenchymal mid inferior kidney?

Parenchymal Kidney Stones: Uncommon but Recognized Entity

Yes, it is uncommon to have a kidney stone located within the renal parenchyma itself, as the vast majority of kidney stones form in the collecting system (calyces, renal pelvis) rather than embedded in the kidney tissue. 1, 2

Typical Stone Locations vs. Parenchymal Stones

Normal stone distribution:

• Kidney stones are most commonly located in the renal calyces (especially lower pole due to gravitational effects and impaired drainage) and the renal pelvis 1
• Stones form when minerals crystallize in urine within the collecting system, not typically within the kidney parenchyma itself 3, 4
• The most common calcium oxalate stones form at Randall's plaque on renal papillary surfaces, which is still within the collecting system 3, 4

Parenchymal calcifications are different:

• True parenchymal stones represent calcified renal parenchymal scars from old granulomatous disease, renal abscess, or hematoma 2
• These appear as densely calcified solitary masses in peripheral kidney locations, often with exophytic projection 2
• They are benign calcified masses without malignant potential and remain stable over time 2

Diagnostic Challenges

Distinguishing parenchymal calcifications from collecting system stones:

• Computed tomography is the most sensitive technique for detecting stones or calcifications (93-96% sensitivity) 1, 5
• Intravenous urography is most sensitive for visualizing the intrarenal collecting system and demonstrating the relationship of calcifications to the collecting system 5
• The diagnosis requires demonstrating whether the calcification communicates with the collecting system 5

Common pitfalls:

• In polycystic kidney disease, parenchymal and cyst wall calcifications are frequent and can be confused with true collecting system stones 5
• Nephrocalcinosis (calcium deposits in renal tissue) implies underlying metabolic disorders but is distinct from typical kidney stones 6
• Medullary sponge kidney can show precaliceal tubular ectasia with calcifications that may appear parenchymal 6, 5

Clinical Implications

Management differs from typical stones:

• True parenchymal calcifications (calcified scars) should be regarded as benign without need for intervention 2
• Long-term follow-up demonstrates complete stability without evidence of growth 2
• If a calcification is truly within the parenchyma and not communicating with the collecting system, it does not require the typical stone treatments (SWL, ureteroscopy, PCNL) 2

When stones appear parenchymal but aren't:

• Stones can become embedded in papillae or appear parenchymal on imaging but still communicate with the collecting system 3
• These require standard stone treatment approaches based on size and location 1