Laparoscopic Injection of Methylene Blue to Discriminate Cyst from Calyceal Diverticulum

Document Type : Case Report


Urology research Center, Tehran University of Medical Sciences, Tehran, Iran



 Renal cysts are sacs of fluid with a thin wall usually with no symptoms and have no connection to the renal calyx. Another renal lesion that can be misdiagnosed with cysts is the calyceal diverticulum with a connection to the renal calyx. The new approach of laparoscopic injection of methylene blue can help the surgeon to distinguish renal cysts from calyceal diverticulum in a patient with no double J (Dj/JJ).

Case presentation
A 52-years patient with a 15 cm lesion underwent laparoscopic surgery of a renal cyst. Surgery was done in the flank position and the peritoneoscopy was performed after cyst reveal. At the bottoms of the cyst, several small cysts were observed so we inject methylene blue to make it clear this lesion was exactly cysts, not calyceal diverticulum. When it was proven that there is no leaking of blue color to the renal calyx through the catheter. The cyst was revealed and was removed and sent for pathology.

In our study, the laparoscopic injection of methylene blue indicated no connection with renal calyx so the lesion is renal cysts.  So it can be a new approach for distinguishing cyst from calyceal diverticulum.


  • Renal cysts are sacs of fluid with a thin wall usually with no symptoms and have no connection to the renal calyx.
  • Methylene blue canprove that there is no leaking of renal calyx through catheter.
  • Methylene blue can consider for distinguishing cyst from calyceal diverticulum.



The kidney is one of the most common sites for the cyst in the body (prevalence about 5%). Kidney cysts are sacs of fluid in the kidneys which are characterized as "simple" cysts with a thin wall (1). They become common as people getting old and are with no symptoms or harm. Because they often don’t cause symptoms are incidentally found by renal imaging including computed tomography (CT) and ultrasonography (2, 3). The prevalence, number, and size of renal cysts are greater in men compared to women and are connected to age, hypertension, and smoke (4). Most renal cysts (sporadic, acquired, or hereditary) arise from parts of nephrons or collecting ducts, while multicystic dysplasia arises before the formation of nephrons (5).
The calyceal diverticulum or pyelocalyceal diverticulum is a urine-containing cystic cavity within the renal parenchyma lining by transitional epithelium and surrounded by muscularis mucosae which are connected to the collecting system (6). The majority of calyceal diverticula can be diagnosed by ultrasound and intravenous urogram (IVU) and retrograde studies are required to confirm calyceal diverticula diagnosis. More often than not, the diverticulum is misdiagnosed as a complex cyst or even as a neoplasm.
The treatment strategy is completely dependent on the exact diagnosis of cysts or calyceal diverticula and it is critical to discriminate cysts from calyceal diverticula. In some patients, there is not possible to place a Double J stent because of the skeletal situation of patients or make the surgery duration shorter. In the current study, we use laparoscopic methylene blue in cysts to ensure there is no contact with the pyelocaliceal system.

Case presentation

A 52-year woman referred to Sina hospital complaining about vague right flank pain and heavy feeling. Her diagnosis was a large flank cyst. She had no family examination, no history of surgery, and no other illness. Abdominal and pelvic computed tomography with and without contrast and simple culture indicated to the 15 cm cyst.
We selected this case and all steps of our study were completely adhere to CARE guidelines. She was the candidate for surgery but there was no certain diagnosis between renal cysts and calyceal diverticulum. In the flank position and through the open access the trocar 15 was embedded. Then peritoneoscopy was performed and 2 trocars 5 were implanted. The colon with strong adhesion was fully medialized. Now the cyst was exposed (Figure 1). The needle was inserted through the skin into the large cyst and sterile methylene blue was injected (Figure 2). The cyst was complete with blue color. The catheter was checked to see whether the blue color enters the urine stream or not (Figure 3). Fortunately, it was completely clear and its roof was unroofed. At the bottoms of the cyst, several small cysts were observed so we inject methylene blue as mentioned above and check for urine color, after approved that the lesions are cyst, the cyst wall was removed. After six weeks and six months, the patient report the satisfying result of surgery with no vague right flank pain or cyst recur in follow-up sonography.

  Figure1. Reveal cyst

Figure 2. Injection of methylene blue