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Renal masses can be broadly categorized into cysts, tumors and inflammatory lesions. Although simple cysts are usually asymptomatic, they occasionally cause flank or abdominal pain, a palpable abdominal mass or hematuria. Malignant masses may produce the same symptoms, or they may associated with paraneoplastic syndromes. Inflammatory lesions are not usually incidental because there is almost always an associated clinical history when symptoms are present. A history of fever with chills or urinary tract infection suggests an infected cyst or an abscess1. With the proper history and interpretation of the renal ultrasonogram and/or CT scan, family physician can correctly identify the majority of renal masses, which are simple renal cysts. They can also identify complex cysts and solid masses, which require further evaluation. Probable benign cysts may undergo surveillance, where as indeterminate or complex cysts should be referred for surgical evaluation.
Renal cysts are common renal mass. Their frequency increase with age and they are present in half the population above the age of 50. The etiology of renal cysts is not known, but it is possible that they form from the epithelial overgrowth of tubules or collecting ducts, with resulting distension of the nephron. This would explain why cysts enlarge over time, and the involvement of adjacent nephrons might explain why thin septations develop2. Elkin and Bernstein classified renal cysts; (1) renal cysts due to dysplasia of the kidney; (2) polycystic disease; (3) cortical cysts; (4) medullary cysts; (5) miscellaneous intrarenal cysts; (6) extraparenchymal renal cysts. Ultrasound criteria for the diagnosis of a simple renal cyst includes (1) Spherical or ovoid shape; (2) absence of internal echoes; (3) presence of a thin, smooth wall that is separate from the surrounding parenchyma; and (4) enhancement of the posterior wall, indicating ultrasound transmission through the water-filled cyst3.
The object of study was to detect the ultrasonic differential diagnosis of renal cysts, because ultrasonography is a uniquely safe and non-invasive means of imaging internal anatomy. Renal cysts are common incidental findings on ultrasonography but may also form part of specific disease process. Differentiation of the patterns of the cystic disease is necessary for diagnosis4.
PATIENTS AND METHODS:
The study was conducted between January 2007 to April 2008 at the department of Radiology and Urology, Chandka Medical College Hospital, Larkana. 100 (Symptomatic or Asymptomatic) patients of either sex with renal cysts who were detected on ultrasonography were included in the study. Along with history, physical examination renal ultrasonography was performed to see the site, size and number of cysts.
A renal ultrasound is a radiological study of the kidneys that can look at the kidneys in cross section. Position of the patient for right kidney scanning supine, left posterior oblique, left lateral decubitus, and prone as needed. For left kidney scanning right lateral decubitus, prone as needed. Different patient positions were used whenever the suggested position does not give the desired results. Just Vision 400 ultrasound machine by Toshiba with 3.5 MHz convex (multi frequency) probe was used for kidneys examination. No preparation was required for ultrasound examination.
From January 2007 to April 2008, hundred patients were included in the study. 72 were males and 28 were females. Male to female ratio was 2.5:1. Age ranges were between 1-100 years (Table-1). Of the one hundred patients forty presented with symptoms but sixty were asymptomatic. Among 40 symptomatic patients the most clinical presentation associated with renal cyst in this study was diabetes mellitus 10 (25%) and abdominal pain 7(17.5%) (Table-2).
Among 100 patients differential diagnosis of renal cyst in 89 (89%) patient simple renal cysts were detected, hydronephrosis in 7 (7%), medical renal disease in 2 (2%), polycystic disease in 1 (1%), hematoma in 1 (1%) were observed (Table-3). Of the 89 patients of simple renal cysts 57 (64%) were cortical cysts, 4 (4.5%) medullary cysts, 22 (25%) parenchymal cysts, 4 (4.5%) Para pelvic cysts, 2 (2.2%) extra parenchymal cysts (Table-4). Different sizes of simple renal cysts were measured ranged from 1mm to 100 mm, 3(03.40%) measures (01-10)mm, 25(28.40%) measures (10-20)mm, 11(12.50%) measures (20-30)mm, 27(30.33%) measures (30-40)mm, 9(10.22%) measures (40-50)mm, 5(05.28%) measures (50-60)mm, 3(03.40%) measures (90-100)mm and 6(06.81%) measures variable sizes (Table-5)
(Fig: ). Cystic criteria were also assessed through 89 patients. Along this series the most frequent type of loculation in various renal cyst was uniloculated 87(98%) and 2(2%) were biloculated. Usually the cysts are solitary but may be multiple. As was seen in this study, 91(91%) cases presented as unilateral simple renal cyst, 9(9%) cases as bilateral simple renal cyst and multiple cysts nine in number. Internal echogenisity of simple renal cyst in this study revealed there were 100(100%) takes all characteristics of simple renal cyst anechoic or echo-free with absence of internal echoes (Table-6). In 89 patients of simple renal cysts concomitant sonographic abnormalities were detected. Fatty liver were the most common concomitant with simple renal cyst during this study (4 Patients). There was one case showed benign prostate. Others each case for renal stone, pleural effusion, enlarged prostate gland, renal enlargement, reduce kidney size, ectopic kidney, renal transplantation and angiomyolipoma (Table-7).
This study was carried out on 100 patients in whom renal cysts were identified sonographically, 72% were male patients and 28% were females. So males were more affected in our study than females. Previous study by Hanna et al confirmed that, the distribution is equal between males and females5. In our series 89% of cases were diagnosed as simple renal cyst which represent the most common differential diagnosis of renal cysts followed by, 7% hydronephrosis, 2% medical renal disease, 1% polycystic kidney disease, 1% hematoma. There was no case presented with renal dysplasia. .Study by Yamagishi et al confirmed that, thorough review of family history can also add valuable information. Differential diagnosis should include multicystic and polycystic kidney disease and structural anomalies such as duplication and calyceal diverticula, tumor, abscess and hematoma may be considered, but they most likely will have internal echoes. Although renal cysts can be seen in chromosomal abnormalities, there are usually other anomalies present6. When cystic lesion is seen in the upper pole, an adrenal origin must also be considered. Finally, a cystic teratoma of the retro peritoneum can be considered.
The youngest patient was 3 years old boy with average size of left kidney showed mild back pressure change with good parenchymal thickness, dilated renal pelvis and ureter down to bladder. Umbilical hernia noted with defect at anterior abdominal wall measures (7mm) with intestinal loops seen passing through. The eldest patient was 95 years old male with bilateral simple parenchymal cyst. The highest incidence of simple renal cyst in 6th and 7th decades of life. While the lowest incidence in 1st and 2nd decades.
Previous studies confirmed that, the pathogenesis of renal cyst is not entirely known. Because of increasing frequency of renal cysts with age (they are found in over 50% of people over 50 years of age). It has been suggested that cyst formation is acquired- a result of the aging process5,7. Vascular changes associated with age affect blood flow to the kidneys. This decreased blood flow causes areas of ischemia or infarct and obstruction of the renal tubules which leads to cyst formation. Another theory suggests that cysts are developmental in origin. During renal organogenesis, the second to fourth generation of uriniferous tubules, resulting in cyst formation 8.
Among 40 symptomatic patients the most clinical presentation associated with renal cyst in this study was diabetes mellitus 10 (25%) and abdominal pain 7(17.5%) they were more frequently associated with simple cyst, there were 60 patients asymptomatic commonly associated with renal cysts.
Previous studies confirmed that, highlight a number of aspects pertaining to simple renal cysts. Firstly, most cases are asymptomatic and are best treated conservatively by regular ultrasound follow up. Lastly, as the natural history of simple cyst is not known, long- term sonographic follow-up is recommended; simple cysts can be the initial manifestation of autosomal dominant polycystic disease in a child9,10.
Sonographic evaluation of renal cyst revealed that simple appearances were most commonly seen in renal cysts and limited polycystic disease and hematoma.
Along this series among 89 patients of simple renal cysts the most frequent type of loculation in various renal cyst was uniloculated 87(98%) and 2(2%) were biloculated.
The major sonographic findings of wall thickness and regularity were thin and regular walls, that more presented in renal cysts.
There were (57 of 89) were cortical cyst, (22 of 89) were parenchymal cyst, (4 of 89) were medullary cyst, (4 of 89) were parapelvic cyst and (2 of 89) were extraparenchymal cyst. Previous study confirmed that, the upper pole is the most common site5.
Usually the cysts are solitary but may be multiple. As was seen in this study, 81(91%) cases presented as unilateral simple renal cyst, 8(9%) cases as bilateral simple renal cyst and multiple cyst nine in number. Previous study confirmed that, the distribution is equal between right and left kidneys5.
Internal echogenisity of simple renal cyst in this study revealed there were (100%) takes all characteristics of simple renal cyst anechoic or echo-free with absence of internal echoes. Previous study confirmed that, many incidental renal masses are discovered on abdominal ultrasound examinations. Ultrasound criteria for the diagnosis of a simple renal cyst include the following: (1) spherical or ovoid shape; (2) absence of internal echoes; (3) presence of a thin, smooth wall that is separate from the surrounding parenchyma; and (4) enhancement of the posterior wall, indicating ultrasound transmission through the water-filled cyst11.
When the ultrasound criteria for a simple cyst are met, the likelihood of malignancy is extremely small. Asymptomatic patients with incidental renal cysts that meet these criteria require no additional evaluation.
Fatty liver were the most common concomitant with simple renal cyst during this study (4 Patients). There was one case showed benign prostate. Others each case for renal stone, pleural effusion, enlarged prostate gland, renal enlargement, reduce kidney size, ectopic kidney, renal transplantation and angiomyolipoma.
Fatty liver were the more frequent concomitant disease in association with simple renal cyst were detected as an incidental sonographic finding during this study. Previous study confirmed that, simple renal cyst has controversy related to hypertension and renal dysfunction. There was (6 of 40) (15%) hypertension patients during this study.
Different sizes of 89 simple renal cysts were measured, 3(03.40%) measures (01-10)mm, 25(28.40%) measures (10-20)mm, 11(12.50%) measures (20-30)mm, 27(30.33%) measures (30-40)mm, 9(10.22%) measures (40-50)mm, 5(05.28%) measures (50-60)mm, 3(03.40%) measures (90-100)mm and 6(06.81%) measures variable sizes. Pervious study confirmed that size range from very small to very large in diameter.
Generally ultrasound detected all renal cysts, while CT scan used to confirm the diagnosis and picked up of peripherally located and cystic masses. Two cases were aspirated under ultrasound guidance, were clear fluid.
The most common differential diagnosis of renal cyst is simple cortical renal cyst with highest incidence in 6th and 7th decades of life. The least common is polycystic kidney disease or hematoma.
Out of this study we believe more that ultrasound is the single cost effective mean in detection of renal cyst.