Dromedary Hump Kidney: Ultrasound, CT, Left Kidney, Symptoms & Mass Differentiation

Conent:

• What is Dromedary Hump Kidney?
• Ultrasound
• CT Scan
• Left Kidney
• Symptoms
• Mass Differentiation

What is Dromedary Hump Kidney?

A dromedary hump is a normal anatomical variant of the kidney, most commonly seen on the lateral border of the left kidney. It is named for its hump-like appearance, resembling the single hump of a dromedary camel. This variation is usually harmless and occurs due to the pressure of the spleen during renal development, which causes a localized bulge in the cortical surface of the kidney.

Dromedary humps are observed in approximately 0.5–1% of the population and are typically unilateral, affecting the left kidney. They do not represent any pathological condition and rarely cause symptoms. However, their appearance on imaging can sometimes mimic renal masses, making it important for radiologists and clinicians to correctly identify this variant to avoid unnecessary interventions.

Ultrasound

On ultrasound, a dromedary hump appears as a smooth, cortical bulge with the same echogenicity as the surrounding renal parenchyma. It is usually located on the lateral aspect of the left kidney, with clear demarcation from the renal sinus. The corticomedullary differentiation is preserved, which helps distinguish it from true renal tumors.

Ultrasound is the first-line imaging modality to identify a dromedary hump, as it is non-invasive, cost-effective, and widely available. The hump is usually incidental, detected during imaging for other reasons such as hematuria, abdominal pain, or routine checkups. Doppler studies may also be used to confirm normal renal blood flow in the area of the hump.

CT Scan

On CT imaging, a dromedary hump presents as a well-defined cortical bulge with attenuation values identical to the normal renal parenchyma. It does not enhance differently after contrast administration, which differentiates it from solid renal masses or tumors. There is no distortion of the renal pelvis or calyces.

CT scans provide a more detailed anatomical view than ultrasound and are particularly useful when there is uncertainty in differentiating the hump from other renal lesions. Multiplanar reconstructions can clearly show the uniformity of renal tissue and the absence of a mass effect, confirming the benign nature of the dromedary hump.

Left Kidney

The dromedary hump predominantly occurs on the left kidney due to the physical pressure of the spleen during renal development. Its location on the lateral border is characteristic, and it usually does not affect renal function or drainage. The right kidney rarely demonstrates this variant.

The left-sided predominance is an important distinguishing feature for clinicians, as it allows radiologists to anticipate and correctly identify the hump during imaging. Knowledge of this variant prevents unnecessary worry or invasive procedures, especially when evaluating incidental renal findings on the left side.

Symptoms

Typically, a dromedary hump is asymptomatic. Most patients are unaware of its presence, and it is usually discovered incidentally during imaging for unrelated issues such as urinary tract infections, hematuria, or abdominal pain.

Rarely, if a patient experiences flank discomfort, it is usually attributable to another underlying renal or urinary condition rather than the hump itself. Because it does not interfere with renal function or drainage, routine follow-up is not required unless imaging is needed for other reasons.

Mass Differentiation

Differentiating a dromedary hump from a renal mass is critical to avoid unnecessary biopsies or surgeries. Key distinguishing features include smooth cortical contour, uniform parenchymal echogenicity on ultrasound, identical attenuation on CT, and absence of abnormal enhancement. Doppler ultrasound can also demonstrate normal blood flow through the hump, confirming its benign nature.

Awareness of the classic location (lateral aspect of the left kidney) and imaging characteristics allows radiologists and clinicians to confidently identify a dromedary hump. Recognizing this variant prevents misdiagnosis, reduces patient anxiety, and avoids unwarranted invasive procedures such as renal biopsy or surgery.