Bilateral renal lymphangiectasia

Discussion

Our patient was diagnosed with bilateral RL based on characteristic radiological findings observed in a contrast-enhanced CT scan. This rare, benign, developmental malformation of renal lymphatics has been documented in the literature under various names, such as RL, renal lymphangiomatosis, renal lymphangioma, renal lymphatic malformation (RLM), peri-pelvic lymphangiectasia, renal sinus polycystic disease, and renal hygroma.³ Renal lymphangiectasia is the preferred term, as it accurately reflects the nature of the disease as a malformation rather than a tumor.^1,5

Lymphangiectasia is usually found in children, most commonly involving the head and neck regions (approximately 70%), followed by the chest and axillary region (20–25%).^4,5 Only about 5% of cases are located in internal organs, with kidneys accounting for a rare 1%.^1,2,4,5 The rarity of the disease limits our understanding of its etiopathogenesis, incidence, prevalence, and natural history.^4,6,8 Clinical presentation and imaging findings are primarily derived from isolated case reports or case series.^3-6

The cystically dilated lymphatics of RL can be in the perirenal, peripelvic, and intrarenal regions.^5,6 Radiologists, playing a crucial role in diagnosis, must be vigilant, as RL may be misdiagnosed as more common cystic lesions, such as hydronephrosis, polycystic kidney disease, and parapelvic cysts.^1,3,5 Proper diagnosis is essential for guiding therapeutic decisions.^4,6,7

The data indicates that RL has an equal incidence in males and females.^1-3,6 Renal lymphangiectasia can manifest in both pediatric and adult populations,with children more frequently presenting with ascites, signifying a more severe form of the disease.^1-3,6,8,9 Renal lymphangiectasia can be focal or diffuse and may be located in the perirenal, peripelvic or intrarenal region in one or both kidneys.^3,5,6,9 By 2022 a total of 104 cases of RL had been reported globally, 5 cases were from Saudi Arabia.⁸ Our cases of RL is bilateral and in an adult, only 33 such cases had been reported earlier.⁸

The etiology and pathophysiology of RL remain elusive, mechanisms including genetic, developmental, or acquired factors were proposed in various case reports.^2,3,5,7-9 A prevailing hypothesis suggests developmental malformations and miscommunication between renal and retroperitoneal lymphatics, resulting in cystic dilatation of lymphatic vessels.^1-4,7,9,10 Some studies noted familial clustering of RL cases, while others proposed inflammation, scarring of lymphatic vessels with obstruction, and dilatation as potential mechanisms.^5,8

Most RLs are asymptomatic; up to 16% of cases are discovered incidentally through radiological imaging.⁸ The most common presenting symptoms include pain in the abdomen or flanks, hematuria, and hypertension.^5,8 Other symptoms may involve proteinuria, fatigue, weight loss, and fever.^1-3,5,8,9 More severe cases can manifest with or be complicated by the rupture of cysts, intracystic hemorrhage, superimposed infection, renal vein thrombosis, ascites, hypertension, or renal failure.^1-3,5,8,9 Polycythemia, hemangioma, and glomerulonephritis have also been reported to coexist with RL.^2,5,8,9 Our case presented with flank pain without any associated complications.

Clinicoradiological correlation rules out other differential diagnoses and confirms the diagnosis of RL.^2,4,5,7 Ultrasonography (USG) and CT with or without contrast enhancement are the most widely used radiological investigations for this purpose.⁵ While earlier, biopsy and surgical pathology were being used for diagnosis, this invasive approach is now discouraged.⁵ Few suspicious cases can be confirmed by needle aspiration and cytological examination of chylous fluid.^3,4,9

Typically, USG reveals anechoic lesions with increased transmission, and thin-walled cysts, with or without septations in the renal sinus or perirenal location.^1,4,7 Computed tomography has emerged as the preferred modality for diagnosing RL. Uncomplicated cases exhibit characteristic findings of well-defined, multiseptated, low-attenuation (0-20HU) lesions in the peripelvic, perinephric, or intrarenal location.^1,4,10 Triple-phase contrast-enhanced CT scans demonstrate no opacification of cysts during the delayed phase, a characteristic finding confirming the diagnosis of RL and distinguishing it from hydronephrosis.^2,3,7,10 On magnetic resonance imaging (MRI), cystic lesions appear hypointense on T1-weighted images and hyperintense on T2-weighted images.^1,5,7 T2-weighted images also reveal increased cortical and decreased medullary intensity.^5,7 Lymphoscintigraphy, a recent introduction, aids in detecting abnormal lymphatic flow.¹ In our case, USG raised suspicion of bilateral cystic lesions in the pelvicalyceal region, which was subsequently confirmed by a CT scan.

Cytological examination of aspirated fluid is reserved for suspicious cases.^1,3 The gross appearance may not be milky or chylous, as it does not involve mesenteric drainage.⁴ Lymph from renal origin characteristically exhibits only a few cells, small amounts of protein, and fat globules with elevated renin levels.^4,7

Several differential diagnoses are considered depending on the age, clinical features, and appearance of the disease. The most common mimickers include hydronephrosis, polycystic disease, multilocular cystic nephroma, lymphoma, and nephromblastomatosis.^1-3,9

Due to rarity, the natural history of the disease is unclear.⁵ Renal lymphangiectasia may have rapid progression, regression, or spontaneous remission.^5,10

The choice of treatment depends on presenting symptoms; however, existing literature does not conclusively recommend one treatment modality over another.⁸ Most asymptomatic cases do not require treatment, and patients with mild symptoms, such as in our case, are managed conservatively.^2,9,10 Analgesics are prescribed for pain, antihypertensives for arterial hypertension, or diuretics to control ascites.^1,8 For large or rapidly growing lesions causing pressure symptoms, percutaneous aspiration with or without sclerotherapy or marsupialization can be performed.^1,2,4,8,10 Close follow-up is required in all cases to monitor potential complications like hypertension, renal vein thrombosis, or renal failure.^3,7,10 For severe, uncontrollable, or complicated cases like renal vein thrombosis or Page kidney, nephrectomy can be considered.^1,3,4,8 However, nephrectomy is usually avoided as it may lead to an increase in the size of lymphatic cysts in the contralateral kidney.^7,9

In conclusion, RL is a rare disease that requires differentiation from other conditions based on characteristic radiological features. Treatment is conservative, with periodic follow-ups for hypertension and renal insufficiency. Radiologists and physicians should be familiar with this rare entity and vigilant in achieving a proper diagnosis and treatment in order to avoid unnecessary and invasive diagnostic and therapeutic modalities.