British Journal of Radiology 74 (2001),595-601 © 2001 The British Institute of Radiology
Pyelocalyceal diverticulum: the imaging spectrum with emphasis on the ultrasound features
V Rathaus
1
O Konen
1
M Werner
1
M Shapiro Feinberg
1
M Grunebaum
2 and
R Zissin
1
1Department of Diagnostic Imaging, Sapir Medical Center and 2Veteran Pediatric Radiologist, Sapir Medical Center, Kfar Saba and Sackler Medical School, Tel Aviv University, Israel
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Abstract
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Clinical and imaging data of 11 patients with pyelocalyceal diverticulum were retrospectively examined. Four patients suffered from ipsilateral flank pain, one from recurrent urinary tract infection and the other six from unrelated symptoms. All patients underwent ultrasound as the initial imaging study. In two cases ultrasound was the only examination performed. Additional imaging studies were obtained in the other nine patients (abdominal radiography in six cases, intravenous urography (IVU) in five and CT in four). Ultrasound suggested the diagnosis of pyelocalyceal diverticulum in eight cases owing to the presence of echogenic and mobile material within the cyst-like lesion. In three cases the ultrasound appearance was similar and indistinguishable from a simple cyst and the diagnosis was made by another imaging study IVU in two cases and CT in one). We suggest that ultrasound examination is the best imaging method for the diagnosis of a pyelocalyceal diverticulum, and no further imaging modalities are required when mobile echogenic material is seen. In uncertain cases, another relatively inexpensive imaging study should be added such as abdominal radiography or IVU.
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Introduction
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Pyelocalyceal diverticulum (PCD) is a relatively uncommon cyst-like lesion, often discovered incidentally during ultrasound examination of the kidneys. Two types are identified: one is related to a minor calyx and usually located in the upper pole, while the other is connected with the pelvis or a major calyx in the central portion of the kidney [1]. The majority of PCDs are small and asymptomatic, and do not require any treatment [1]. PCD may rarely cause loin pain, urinary tract infection (UTI), renal colic, pyuria, haematuria or hypertension [2]. Mobile calculi and milk of calcium are characteristic findings in PCD [1, 3, 4]. However, the diagnosis may sometimes be difficult and more than one imaging study is performed. We present the imaging spectrum of PCD in 11 patients, with the emphasis on ultrasound findings.
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Materials and methods
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A retrospective review of the clinical data and imaging studies of 11 patients (6 female, 5 male) diagnosed as having PCD over a 6-year period was undertaken (Table 1
). Patient age ranged from 13 years to 67 years (mean 30 years). Four patients suffered from ipsilateral symptoms originating from the urinary tract and another patient had recurrent UTI. The other six patients were examined for symptoms unrelated to the urinary tract: diffuse abdominal pain (three patients), hypertension (one patient), anaemia (one patient) and fever of unknown origin (one patient).
The ultrasound images of all these patients were reviewed to evaluate the configuration of the lesion, the presence of echogenic material or calcifications and whether there was any positional change. Conventional abdominal radiographs were obtained in six cases. Intravenous urography (IVU) was performed in five of these cases. Conventional non-helical CT was performed in four cases with 5 mm or 10 mm collimation, at intervals of 5 mm or 10 mm, respectively, through the kidneys. Unenhanced and contrast enhanced images were obtained in all cases. Delayed CT images (15–30 min after injection) were obtained in three cases. All CT images were reviewed for the size and location of the cystic lesion, the presence of a communication with the collecting system and for the mobility of the calcifications. The average time interval between the ultrasound and the other imaging examinations was 16 days (range 1–60 days) (Table 1
).
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Results
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Table 1 shows the relevant clinical and imaging data of the 11 patients. Renal ultrasound (RUS) was the initial examination in all cases, and suggested the diagnosis in eight cases. In case 10 the echogenic material appeared after 1 year of follow up. RUS showed a cystic lesion 13–35 mm in diameter (mean 21.7 mm). In seven cases the lesion was located in the upper pole (cases 1–7) and in four within the mid-portion of the kidney (cases 8–11). RUS was the only examination in two cases (cases 7 and 11). In four cases the ultrasound appearance was that of a simple cyst (Figures 1a and 5a), in one of them echogenic material was identified within the cyst-like lesion on a follow-up examination 1 year later (case 10). Echogenic mobile foci were discovered in the cyst-like lesion of the other seven cases, with an acoustic shadow in five of them (cases 1, 4, 7, 8 and 11) (Figure 2a). In three cases, the classic ultrasound appearance of milk of calcium was demonstrated and confirmed on abdominal radiographs (cases 1, 3 and 4) (Figures 3a,b). In one case (case 8), an associated linear mural calcification was seen in the bilobed cyst-like lesion with mobile echogenic material (Figure 4a).
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Figure 1. Case 10: 15-year-old female with right abdominal pain. (a) Sagittal ultrasound of the right kidney. A simple cyst with posterior enhancement in the mid-portion. (b) Intravenous urography. Pyelocalyceal diverticulum connected to the middle calyx of the right kidney.
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Figure 2. Case 4: 47-year-old male with diffuse abdominal pain. (a) Transverse renal ultrasound of the right kidney. Cyst-like lesion with mobile hyperechogenic material with a weak posterior acoustic shadow. (b)Supine abdominal radiograph. Multiple small round calcifications (milk of calcium) in the right upper abdomen. (c) Right lateral decubitus abdominal radiograph. Linear calcifications in the right abdomen.
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Figure 3. Case 7: 24-year-old female with right lower abdominal pain. (a) Supine ultrasound of the right kidney. Hyperechoic lesion in the upper pole. (b) Left lateral decubitus ultrasound shows the same lesion at the upper pole with gravity-dependent hyperechogenic material. A posterior acoustic shadow is seen.
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Figure 4. Case 8: 41-year-old female with hypertension. (a) Transverse ultrasound image of the right kidney. A bilobed cyst-like lesion with hyperechogenic mobile material in the lateral part and posterior acoustic shadow. (b) Pre-contrast supine CT shows a bilobed hypodense mass with mobile gravity-dependent calcified material in the lateral portion. (c) Pre-contrast prone CT: change in position of the calcified material in the lateral part of the bilobate cyst.
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Figure 5. Case 9: 35-year-old male with fever of unknown origin. (a) Longitudinal ultrasound of the left kidney. Simple cyst in the mid-portion. (b) Pre-contrast CT shows a hypodense lesion in the left kidney. (c) After contrast injection no opacification is seen in the lesion. (d) 15 min after injection there is now contrast material within the diverticulum.
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Abdominal radiographs detected small, round calcifications in three cases (cases 1, 3 and 4) (Figure 2b). Upright or lateral decubitus radiographs confirmed the gravity dependence of these calcifications, and the pathognomonic appearance of the half-moon shape of milk of calcium was seen in one of them (case 4) (Figure 2c).
On IVU, the cyst-like lesion was opacified by contrast medium in four cases, confirming its connection with the pelvicalyceal system (cases 3, 5, 6 and 10) (Figure 1b).
On CT, mobile gravity-dependent stones were found in four cases (cases 1, 2, 8 and 9) (Figures 4b,c). In one of them, an additional linear calcification was seen in the lesion (case 8). Connection with the collecting system was demonstrated on delayed images in 2 cases (cases 8, 9) (Figures 5b–d).
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Discussion
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PCD is a urine-containing cavity within the renal parenchyma, communicating with the collecting system through a narrow channel. It is lined by transitional epithelium and surrounded by a layer of muscularis mucosae [1]. Two main types of diverticula are recognized: Type 1, the most common, which is related to a minor calyx; and Type 2, which communicates with the renal pelvis or a major calyx. This last type is larger, tends to be symptomatic and is located in the central portion of the kidney [1]. In 7 of the 11 patients in this series the PCD was in the upper pole and in 4 patients in the mid-portion of the kidney. The incidence of PCD is 2.1 to 4.5 per 1000 IVUs [1]. They occur equally in both sexes, and with the same frequency on both sides. The diverticula are bilateral in 3% of cases [1]. The aetiology is probably congenital, resulting from failure of regression of the third or fourth division of the ureteric buds of the Wolffian duct [1]. PCD may rarely be acquired as a result of an infection or passage of a small stone [5].
Up to 39% of these diverticula contain calculi or milk of calcium, secondary to stasis and/or infection [3–5]. Echogenic material was present in the diverticula in the majority of cases in this series. The characteristic appearance of milk of calcium [4, 6] was demonstrated in three of these eight cases (Figures 3a,b). Milk of calcium is a fine colloidal suspension of precipitated calcium salts (carbonate, phosphate and oxalate) and may be radiopaque or radiolucent [4]. Its pathogenesis is unclear, perhaps obstruction or low-grade inflammation being a factor in its formation [4].
Ultrasound examination suggests the diagnosis of PCD and it has a variable appearance [3, 5, 7]; the diverticulum may appear as a cyst-like lesion, indistinguishable from a simple cyst [3]. Recognition of mobile echogenic material within such a cyst-like structure is considered characteristic of milk of calcium [3, 4, 8]. A cyst-like mass with milk of calcium is presumed to be a PCD [8]. When echogenic material is found within a cyst-like mass it is therefore important to scan in different positions to demonstrate the gravitational change of this content [3, 4]. In these cases the diagnosis is evident, without needing another imaging study.
In the presence of a stone, differential diagnosis with an obstructed calyx is difficult, and main abdominal radiography, IVU or CT are helpful [3]. Abdominal radiographs confirm the diagnosis of PCD in the presence of opaque milk of calcium [5, 6] by a characteristic meniscus-like, half-moon-shaped calcification that changes position on upright or lateral decubitus radiographs [6] (Figure 2c). On IVU, most calyceal diverticula will opacify owing to the connection with the collecting system. This occurs later in the examination, since the diverticulum is filled in a retrograde fashion from its connecting calyx or pelvis [9]. However, when the neck of a PCD is obstructed, the diverticulum will not opacify and it is impossible to distinguish between a renal cyst and an obstructed calyceal diverticulum.
CT has an important role in the presence of a complicated cystic mass diagnosed by RUS without the characteristic features of PCD. The demonstration of the layering of contrast medium on delayed images is pathognomonic of these lesions [2]. It is important to differentiate PCD from a renal tumour when only slight opacification is seen after contrast medium injection [2]. The patency of the diverticulum is demonstrated by the gradual opacification on delayed images (Figures 5b–d).
Abdominal ultrasound is often performed for various non-specific abdominal symptoms and is usually the first imaging modality to diagnose a PCD. The diagnosis becomes evident on ultrasound in the presence of mobile echogenic material in these cystic lesions. Awareness of the ultrasound appearance of PCD is important to reassure the clinician of its benignity and to obviate the need for other imaging studies.
Received for publication November 20, 2000.
Accepted for publication January 24, 2001.
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References
|
|---|
-
Wulfsohn MA. Pyelocaliceal diverticula. J Urol 1980;123:1–8.[Medline]
-
Gayer G, Apter S, Heyman Z, Morag B. Pyelocalyceal diverticula containing milk of calcium—CT diagnosis. Clin Radiol 1998;53:369–71.[Medline]
-
Jacobs RP, Kane RA. Sonographic appearance ofcalculi in renal calyceal diverticula. J Clin Ultrasound 1984;12:289–91.[Medline]
-
Patriquin H, Lafortune M, Filiatrault D. Urinary milk of calcium in children and adults: use of gravity-dependent sonography. AJR 1985;144:407–13.[Abstract/Free Full Text]
-
Siegel MJ, MacAlister WH. Calyceal diverticula in children: unusual features and complications. Radiology 1979;131:79–82.[Abstract]
-
Healey T, Way BG, Grundy WR. Milk of calcium in calycine diverticula. Br J Radiol 1980;53:845–52.[Abstract/Free Full Text]
-
Medani CR, Dunne MG. Ultrasonic appearance of pyelogenic cysts. South Med J 1983;76:1556–8.[Medline]
-
Widder DJ, Newhouse JH. The sonographic appearance of milk of calcium in renal caliceal diverticuli. J Clin Ultrasound 1982;10:448–50.[Medline]
-
Middleton AW Jr, Pfister RC. Stone-containing pyelocaliceal diverticulum: embryogenic, anatomic, radiologic and clinical characteristics. J Urol 1974;111:2–6.[Medline]
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Abstract
Introduction
