CT and Ultrasound Diagnosis of Low-Grade Appendiceal Mucinous Neoplasm with Chronic Torsion: A Case Report with Systematic Review of the Literature

The appendix is a small, finger-like pouch attached to the beginning of the large intestine. For most people, it is a silent organ that causes trouble only when it becomes inflamed, a condition known as appendicitis. However, the appendix can also develop a rare type of slow-growing tumor that fills the organ with a thick, jelly-like substance called mucus. When this happens, the appendix swells like a water balloon, becoming a cystic mass. If this swollen organ twists on its own base, it cuts off its blood supply, a process called torsion. While a sudden twist causes immediate, severe pain, a slow, partial twist can linger for years, slowly damaging the tissue without obvious warning signs. Understanding how these slow twists appear on medical scans is crucial because if the swollen appendix bursts, the jelly-like tumor cells can spread throughout the abdomen, creating a serious condition that is very difficult to treat.

A team of doctors in China recently shared the story of a 48-year-old woman who helped them understand this slow-moving danger. Her journey began in late 2022, when a routine scan for a different health issue accidentally revealed a strange, tube-shaped cyst in her lower right abdomen. At that time, the cyst was about the size of a small grapefruit, with a thin, smooth wall. The doctors noticed a subtle spiral pattern in the blood vessels near the base of the appendix, a sign that the organ had already begun to twist slightly. Over the next few years, the woman experienced mild, recurring pain, but she did not seek immediate help. The medical team, however, kept a close watch. By late 2024, a new scan showed the cyst had grown slightly larger, and the wall had begun to thicken and develop faint, chalky spots. The spiral pattern of the blood vessels remained visible, confirming the organ was still twisting, though the rotation had tightened.

The situation changed dramatically in early 2026. The woman arrived at the hospital with sharp, acute pain. A new scan showed the cyst had grown to over 11 centimeters in length, and the wall was now thick and covered in distinct, nodular calcium deposits. The inflammation around the organ had become so intense that the tell-tale spiral pattern of the blood vessels, which had been clear for years, was now hidden by the swelling. An ultrasound scan provided a different view, showing the inside of the cyst filled with a dense, cloudy texture that looked like a snowstorm, a sign of the thick mucus inside. Crucially, the scan showed no blood flow in the wall of the cyst, indicating that a large section of the organ had died from lack of blood.

Emergency surgery revealed the full extent of the damage. The appendix had twisted a full two complete turns, or 720 degrees, in a clockwise direction. The middle and far end of the organ were dark purple and dead, while the base remained alive. The surgeons removed the organ safely, and laboratory analysis confirmed it was a low-grade tumor confined within the appendix walls, with no signs that it had spread. This case is significant because it tracks the entire life cycle of a twisted, tumor-filled appendix over three and a half years. It shows that even when the classic signs of twisting disappear on a scan due to severe inflammation, the history of the organ's growth and the appearance of its wall can still tell the story. By watching how the wall thickened and calcified over time, doctors can identify a slow, dangerous twist before it leads to a catastrophic rupture, allowing for a timely and life-saving intervention.