Teaching Case

We present a case of a 67-year-old male patient who underwent partial right nephrectomy for resection of a solid renal mass. A follow-up abdominal and pelvic CT examination was performed 12 months later and a fat-fluid level inside the bladder was identified, with hypodense material located above the dependent fluid.

We present a case of a 67-year-old male patient who underwent open upper-pole partial right nephrectomy for resection of a solid renal mass, measuring 5 cm, diagnosed during a routine ultrasound (Fig 1).
A CT examination was then performed (Figs 2, 3) and revealed a slightly heterogeneous right kidney mass, with central areas of low attenuation probably due to necrosis (Fig 2a). The lesion was hypovascular, with only slight enhancement after contrast administration.
No intra-operative complications were reported. Pathologic examination revealed a renal cell carcinoma, papillary cell type (type I). The post-operative period was uneventful and the patient experienced no symptoms.
A routine follow-up abdominal and pelvic CT examination was performed 12 months and 18 days after the surgery, revealing changes from the partial nephrectomy (Fig 4), without perinephric collections or signs of tumour recurrence. A level inside the bladder was identified, with hypodense material located above the dependent fluid (Fig 5). A region of interest based on attenuation confirmed the presence of fat.

Chyluria is a rare condition. In endemic regions, it is mostly due to infection and consequent obstruction of the renal lymphatic vasculature by filariasis [1]. On the other hand, in Western countries this condition is usually secondary to nonparasitic causes such as tumours, abscesses, tuberculosis, pregnancy and congenital conditions [2]. Few cases of chyluria after partial nephrectomy have already been reported [2-5], but the frequency might increase in the future as nephron-sparing surgery for renal masses increasingly becomes the first choice of treatment, in order to reduce the risk of chronic renal insufficiency [2]. To the best of our knowledge, this case is the first reporting chyluria after partial nephrectomy for a papillary renal cell carcinoma.
Chyluria after partial nephrectomy likely occurs as a result of lymphatic injury with formation of a fistulous connection with the collecting system, either at a microscopic or macroscopic level [3]. This hypothesis would explain why this complication more often occurs in association with partial nephrectomy (leaving components of the renal collecting system and renal lymphatic vessels) than with radical nephrectomy (where all these components are removed) [4]. Besides, this theory also justifies why this complication occurs most commonly after left partial nephrectomy than with right partial nephrectomy: the drainage of the lymphatic vessels around the kidneys is made to the para-aortic lymph nodes, which are located nearer to the left kidney and therefore more amenable to injury during surgery [2].
Patients with chronic chyluria can develop symptoms related with hypoproteinemia, hypolipidemia, and loss of immune competence [6]. In asymptomatic patients, conservative treatment with a diet rich in medium-chain fatty acids should be the first option. However, it is less effective than more invasive options like endoscopic sclerotherapy [7] and renal pedicle lymphatic disconnection [8], that should be considered in symptomatic or long-term asymptomatic chyluria.