bubble_chart Overview

Pancreatic cysts include true cysts, pseudocysts, and cystic tumors. True cysts encompass congenital simple cysts, polycystic disease, dermoid cysts, retention cysts, etc., with an epithelial lining on the inner wall of the cyst. Cystic tumors consist of cystic adenomas and cystic carcinomas. Pseudocysts have a fibrous tissue wall without epithelial lining and are the most common type of pancreatic cysts in clinical practice. This section focuses solely on pancreatic pseudocysts.

bubble_chart Etiology

A pancreatic pseudocyst is a cyst formed when spilled blood and pancreatic fluid enter the peripancreatic tissues or, in rare cases, become encapsulated within the lesser omental sac. The difference between a pseudocyst and a true cyst lies in the fact that the latter originates within pancreatic tissue, with the cyst located inside the pancreas and its inner lining composed of ductal or acinar epithelial cells. In contrast, the former is formed when surrounding tissues encapsulate the fluid, creating a cyst wall devoid of epithelial cells, hence the name "pseudocyst."

Approximately 75% of pseudocyst cases result from acute pancreatitis, about 20% occur after pancreatic trauma, and 5% are caused by pancreatic cancer. One study reported 32 cases of pseudocysts, of which 20 developed after acute pancreatitis, 3 followed abdominal trauma, 8 had no clear disease cause, and 1 formed due to compression by a pancreatic fibrofleshy tumor. Among the 20 cases post-acute pancreatitis, the earliest cyst appearance was one week after onset, the latest was two years, with most occurring within 3–4 weeks.

Pancreatic fluid containing various digestive enzymes leaks from necrotic pancreatic tissue into the retroperitoneal space around the pancreas, triggering an inflammatory reaction and fibrin deposition. Over one to several weeks, a fibrous membrane forms, with the posterior peritoneum constituting the anterior wall of the cyst. Alternatively, pancreatic fluid may directly seep into the lesser omental sac, where the Winslow's foramen is often sealed by inflammation, leading to cyst formation within the lesser sac. Sometimes, pancreatic fluid spreads along tissue planes to form cysts in unusual locations, such as the mediastinum, spleen, kidney, or groin.

Howard and Jorden classified pancreatic cysts based on their disease causes: (1) Post-inflammatory pseudocysts: seen in acute or chronic pancreatitis. (2) Post-traumatic pseudocysts: resulting from blunt or penetrating trauma or surgical injury. (3) Tumor-induced pseudocysts. (4) Parasitic pseudocysts: caused by roundworms or hydatid cysts. (5) Idiopathic or unknown causes.

bubble_chart Pathological Changes

Pancreatic necrosis, pancreatic juice, and blood caused by pancreatic inflammation or trauma can form an abdominal mass around the pancreas, in the greater omentum, stomach, and lesser omentum, stimulating surrounding tissues and leading to connective tissue proliferation. If no purulent infection occurs, a fibrous cystic wall may form. Animal experiments show that pseudocyst wall formation takes 4 weeks, while in humans, it requires at least 6 weeks. A typical pseudocyst communicates with the main pancreatic duct. Due to the secretory pressure of pancreatic juice within the cyst, it can continuously expand outward and persist.

Approximately 80% of pancreatic pseudocysts are solitary and vary in size, generally with a diameter of around 15 cm. Smaller ones may be less than 3 cm, while larger ones have been reported to hold up to 5000 ml. The cystic fluid is alkaline and contains proteins, mucus, cholesterol, and red blood cells. Its color varies, ranging from clear yellow to chocolate-like turbid fluid. Although amylase levels are elevated, there are generally no activated enzymes present.

Due to inflammatory reactions, the cyst wall of a pseudocyst may develop adhesions, with necrotic tissue often adhering to the surface. As granulation tissue forms, the cyst wall thickens continuously. During expansion, the cyst can grow in any direction. If activated pancreatic enzymes enter the cyst and erode blood vessels in the wall, intracystic hemorrhage may occur. Becker reported that when a cyst is infected, 70–90% of cases experience fatal cyst rupture or hemorrhage due to pancreatic enzymes eroding blood vessels and the cyst wall. Pseudocysts, especially those in the pancreatic head, may erode the digestive tract and form internal fistulas. Cysts in the pancreatic tail that involve the splenic artery can cause intra-abdominal hemorrhage. Large pseudocysts may compress adjacent organs, leading to compressive symptoms.

It is generally believed that pancreatic pseudocysts are more common in the body and tail of the pancreas. However, with the widespread use of B-mode ultrasound imaging, the detection rate of pseudocysts in the pancreatic head has significantly increased. Sugawa and Walt reported that 50% of pseudocysts are located in the pancreatic head.

During pancreatic inflammation or after pancreatic duct injury, pancreatic fluid and effusion may diffuse along the retroperitoneal space, forming ectopic pseudocysts. For example, they may extend through the diaphragmatic hiatus into the posterior mediastinum, forming mediastinal cysts or even cervical cysts. Alternatively, they may descend along the bilateral paracolic gutters, forming cysts in the inguinal or vulvar regions.

bubble_chart Clinical Manifestations

A few pseudocysts are asymptomatic and are only discovered during B ultrasound examinations. In most cases, clinical symptoms are caused by the compression of adjacent organs and tissues by the cyst. Approximately 80–90% of cases experience abdominal pain. The pain is mostly located in the upper abdomen, and its extent is related to the position of the cyst, often radiating to the back. The pain occurs due to the cyst compressing the gastrointestinal tract, retroperitoneum, celiac plexus, as well as inflammation of the cyst and the pancreas itself. Nausea and vomiting occur in about 20–75% of cases; decreased appetite is seen in approximately 10–40%. Weight loss is observed in about 20–65% of cases. Fever is usually low-grade. Diarrhea and jaundice are relatively rare. If the cyst compresses the pylorus, it can lead to pyloric obstruction; compression of the duodenum can cause duodenal stagnation and high intestinal obstruction; compression of the common bile duct can result in obstructive jaundice; compression of the inferior vena cava can lead to symptoms of inferior vena cava obstruction and lower limb edema; compression of the ureter can cause hydronephrosis, among other complications. Pancreatic pseudocysts in the mediastinum may present with cardiac, pulmonary, and esophageal compression symptoms, such as chest pain, back pain, dysphagia, and jugular vein distension. If the pseudocyst extends to the left groin, scrotum, or rectouterine pouch, symptoms of rectal and uterine compression may occur.

During physical examination, a mass can be palpated in the upper abdomen or left hypochondrium in about 50–90% of patients. The mass is spherical, smooth-surfaced, rarely nodular, but may have a fluctuant sensation, limited mobility, and is often tender.

bubble_chart Diagnosis

In cases of persistent upper abdominal pain, nausea, vomiting, weight loss, and fever following acute pancreatitis or pancreatic trauma, and when a cystic mass is palpable in the abdomen, the possibility of pseudocyst formation should be considered first. Timely diagnostic tests should be conducted to confirm the diagnosis.

1. Hematuria Amylase Measurement: Pancreatic enzymes from the cyst can be absorbed through the cyst wall and appear in the hematuria, leading to grade I to grade II increases in serum and urinary amylase levels. However, reports indicate that amylase levels may not rise in approximately 50% of cases. Generally, serum amylase remains elevated in pseudocysts caused by acute pancreatitis, whereas it is often normal in those caused by chronic pancreatitis.
2. Ultrasound Examination: Ultrasound is a simple and effective method for diagnosing pancreatic pseudocysts. Typically, a clearly defined hypoechoic area can be detected in the upper abdomen. Ultrasound is particularly useful for differentiating between solid masses and cysts, with a diagnostic accuracy rate of 73–91% for pancreatic pseudocysts. Dynamic ultrasound monitoring can track changes in cyst size. Additionally, under ultrasound guidance, cyst fluid can be aspirated for generation and transformation and cytological examination.
3. CT Examination: On CT scans, pancreatic pseudocysts appear as smooth-edged, round or oval areas of uniformly reduced density. If a gas-fluid level is observed on CT, it suggests the formation of an infected abscess.
4. X-ray Examination: Barium meal X-ray examination also has localizing value for pancreatic pseudocysts. Besides ruling out intraluminal gastrointestinal lesions, it can reveal signs of compression and displacement of surrounding organs by the cyst. For example, a large pseudocyst behind the stomach may show forward displacement of the stomach on barium imaging, with possible compression of the lesser curvature. Pseudocysts in the pancreatic head can widen the duodenal loop and displace the transverse colon upward or downward. Abdominal plain films may occasionally reveal pancreatic calcifications.
5. ERCP: ERCP can confirm the presence and location of the cyst and help differentiate it from pancreas cancer. ERCP findings in pseudocysts include cyst filling, obstruction of the main pancreatic duct (with a conical or abrupt termination), compression and displacement of the common bile duct, and non-filling of localized branches in non-communicating cysts. However, about half of pseudocysts do not communicate with the main pancreatic duct, so a normal pancreatogram does not rule out the diagnosis. ERCP can also detect the presence of fistulas. However, since ERCP may induce secondary infection or spread inflammation, it should not be routinely performed in cases where the diagnosis is already confirmed.
6. Selective Stirred Pulse Angiography: Selective stirred pulse angiography has definitive diagnostic value for pseudocysts, as it can reveal the lesion site. The cyst area appears as an avascular zone, with adjacent proximal bleeding vessels showing displacement or deformation. This examination can accurately diagnose vascular invasion, identify the presence and source of bleeding, and determine whether a pseudo stirred pulse aneurysm exists within the cyst wall. Angiography is more valuable than ultrasound or CT for assessing whether a pseudocyst has invaded the spleen.

bubble_chart Treatment Measures

(I) Surgical Treatment of Pancreatic Pseudocysts The primary treatment for pancreatic pseudocysts is surgical intervention. Pseudocysts often persist and enlarge due to their communication with pancreatic duct branches and functional pancreatic tissue. Except for a few small cysts that may resolve spontaneously, approximately 85% of pseudocysts require surgical treatment.

1. Timing of Surgery Most experts recommend delayed surgery to allow sufficient time for the cyst wall to develop a mature fibrous membrane. Premature surgery often results in fragile cyst walls that cannot be effectively sutured, leading to postoperative anastomotic leaks. The optimal approach involves regular B-ultrasound follow-ups during the observation period to monitor whether the cyst resolves or enlarges. If the cyst is found to enlarge or fails to resolve spontaneously after 7 weeks, surgery should be performed.

2. Surgical Approaches Common surgical methods include three categories:

(1) Cystectomy: This is the most ideal method but is mostly suitable for smaller cysts in the pancreatic tail. For larger cysts, this procedure is more challenging.

(2) Cyst Drainage: Historically, external drainage was considered the preferred method for treating pancreatic pseudocysts. However, due to the high incidence of pancreatic fistulas post-external drainage, most scholars now favor internal drainage. Complications following external drainage are numerous, including pancreatic fistula, intra-abdominal abscess, pancreatitis, cyst recurrence, and hemorrhage, in descending order of frequency. Shatney and Lillehei reviewed 119 cases of surgically treated pancreatic pseudocysts and concluded that internal drainage has lower mortality and complication rates.

The preferred internal drainage method is cyst-gastrostomy, which promotes cyst resolution. For cases unsuitable for cyst-gastrostomy, the Roux-en-Y method can be used to drain the cyst into the jejunum or duodenum.

(3) Pancreatectomy: Pancreatectomy is typically performed when there is severe pancreatic disease or malignancy. Procedures include pancreaticoduodenectomy, distal pancreatectomy, or total pancreatectomy.

(II) Other Drainage Methods

1. Percutaneous Aspiration and Percutaneous Catheter Drainage (1) Under CT or B-ultrasound guidance, cyst fluid can be aspirated via puncture, resulting in cyst resolution in about 30% of cases. The main drawback is fluid reaccumulation, necessitating repeated aspirations. (2) During needle aspiration, a drainage catheter can be percutaneously placed to avoid repeated aspirations, particularly suitable for pseudocysts communicating with the pancreatic duct. When no fluid drains from the catheter, it often indicates fistula closure, and drainage can be discontinued. However, catheter blockage should be ruled out before removal. Percutaneous catheter drainage is effective for both infected and non-infected pseudocysts, with success rates of 67–91%. VanSonnenberg et al. reported treating 101 pseudocyst cases with this method, achieving success rates of 90.1% for infected cysts and 86% for non-infected cysts, with an average drainage duration of 19.6 days. The recurrence rate after catheter drainage was only 4%, lower than that after surgical drainage. To prevent infection, they recommended regular catheter irrigation.

2. Endoscopic Drainage If the pseudocyst is adjacent to the stomach or chest wall (specifically, the cyst wall is ≤1 cm from the gastrointestinal lumen on CT or ultrasound), endoscopic drainage can be performed. The method involves using a thermal puncture needle or laser under endoscopy to penetrate the gastric or duodenal wall and cyst wall, followed by placing a nasocystic catheter for continuous drainage. Cremer et al. performed endoscopic duodenal or gastrocystostomy, achieving successful drainage in 96% and 100% of cases, respectively, with recurrence rates of only 9% and 19%. Some advocate a transduodenal papilla approach, placing a catheter into the pseudocyst via the ampulla of Vater.

(3) Drug Therapy Somatostatin has a significant inhibitory effect on pancreatic exocrine secretion. The synthetic somatostatin analogue Sandostatin (octreotide) has a long half-life in vivo and can promote fistula closure in patients with pancreatic fistulas. Lansden et al. administered Sandostatin to 4 patients with pancreatic fistulas following pseudocyst drainage and 1 patient after pancreatic cancer resection. The initial dosage was 50μg twice daily, gradually increased to 150μg twice daily, and continued for 2–6 weeks. By the second day of treatment, the average fistula drainage volume decreased by 52%, and by the third day, it decreased by 70%. All fistulas closed within 7–44 days. No significant side effects were observed.

bubble_chart Complications

Sankaran and Walt reviewed 131 cases of pancreatic pseudocysts and found that 30% of the cases were complicated by infection, involvement of adjacent blood vessels or viscera, and perforation.

1. Secondary infection: This is the most common and severe complication of pseudocysts. The patient's condition deteriorates rapidly, with severe toxemia. If surgery is deficient at this stage, it often rapidly progresses to pancreatic abscess and sepsis, almost invariably leading to death.
2. Pancreatic ascites pseudocyst: Pancreatic fluid leaks from a fistula or fissure into the abdominal cavity, irritating the peritoneal membrane and causing ascites. Blockage of peripancreatic lymphatic vessels leading to lymphatic extravasation can also cause ascites. Normally, the peritoneal membrane can absorb large amounts of fluid, but in pancreatic ascites, due to fibrin exudation, fibrous tissue hyperplasia, inflammatory cell infiltration, and elastic fiber degeneration, the fluid cannot be absorbed in large quantities and accumulates in the abdominal cavity.
3. Pancreatic pleural effusion: Approximately 50% of pancreatic pleural effusions coexist with pancreatic pseudocysts. If pancreatic fluid from the cyst diffuses into the thoracic cavity through diaphragmatic lymphatic vessels, irritating the pleural membrane or forming a fistula between the cyst and the thoracic cavity, pleural effusion can occur. The effusion is mostly on the left side.
4. Hemorrhage: Hemorrhage is a rare but most dangerous complication of pseudocysts. Bleeding can occur due to: (1) rupture of blood vessels within the pseudocyst; (2) erosion of the gastrointestinal wall by the cyst; (3) concurrent portal or splenic vein obstruction leading to esophageal variceal rupture; (4) erosion of the biliary tract by the cyst causing bleeding; (5) rupture of a pseudoaneurysm. In cases of intracystic hemorrhage, the cyst rapidly enlarges, and a bruit may be heard. Therefore, if the cyst suddenly enlarges with systemic signs of blood loss, prompt angiography should be performed, often necessitating emergency surgery, including cystectomy or opening the cyst to ligate the bleeding vessels and perform cyst drainage.
5. Spleen involvement: Patients with pancreatic pseudocysts may also have spleen involvement, possibly due to: (1) erosion of the spleen by the pancreatic pseudocyst; (2) digestive action of pancreatic fluid leaking from the cyst on the spleen; (3) inflammation of ectopic pancreatic tissue within the spleen; (4) concurrent splenic vein thrombosis leading to liquefaction of infarcted areas in the spleen. In such cases, early splenectomy should be performed, and distal pancreatectomy should be considered whenever possible.
6. Cyst rupture and perforation: Pancreatic pseudocysts may spontaneously perforate or rupture into adjacent viscera, often complicated by gastrointestinal bleeding. Rupture of pancreatic pseudocysts into the stomach, duodenum, or colon may not necessarily cause symptoms and may not pose a danger to the patient, as it can provide effective drainage. However, if the cyst ruptures into the abdominal cavity, the mortality rate is extremely high. In such cases, patients often experience shock, with a mortality rate of 18–80%.
7. Others: (1) Jaundice: Obstructive jaundice can occur due to compression of the common bile duct by the pseudocyst. (2) Diarrhea: Pancreatic pseudocysts can sometimes cause severe diarrhea.