Just How Common Are the 'Rare' Complications of COVID-19?

The list of common COVID-19 symptoms hasn’t changed much over the course of the pandemic: fever, cough, fatigue, congestion, loss of smell and taste, etc. But some people with the virus can also experience symptoms and complications that many others don’t.

Now, new research published in the journal Medicina breaks those rare complications down. For the study, researchers analyzed data from 55 research articles and 42 case studies, looking at four major organ systems to see how they were impacted by someone having COVID-19.

After the analysis, the researchers came up with a list of atypical COVID-19 complications, as well as how often they happened in patients.

Prevalence of Atypical COVID-19 Complications

The researchers grouped complications by the organ system impacted: the gastrointestinal system, neurological system, renal system, and cardiovascular system. Here’s what they found—and what it means in simple terms.

Gastrointestinal System Complications

Seven research studies highlighted several gastrointestinal symptoms:

• Pancreatitis (1%): Inflammation of the pancreas
• Ogilvie-like syndrome (1.9%): Sudden and unexplained paralysis of the colon
• Yellow discoloration of the bowel (2.23%): Yellow bowel movements
• Clostridium difficile colitis (3.8%): A disruption of healthy bacteria in the colon
• Acute cholecystitis (3.8%): Gallbladder inflammation
• Bowel ischemia/infarction (4%): Lack of blood flow to the small intestine
• Hepatic Ischemia/necrosis (7.4%): A condition where the liver doesn’t get enough blood or oxygen
• GI bleeding (10.6%): Bleeding in the gastrointestinal tract
• Pneumatosis/portal venous gas (20%): Gas in the intestines
• Bile stasis (54%): The slowing or stalling of bile from the liver
• Ileus (55.8%): Trouble with the bowel contracting as it should
• Transaminitis (67.3%): An elevated level of certain liver enzymes in the blood

To learn more about the outcomes of these symptoms, researchers turned to case reports. Among 19 patients with gastrointestinal complications from COVID observed in 14 case reports, nine patients died, five were cured, and four were still hospitalized and undergoing treatment when the study period ended.

Neurological System Complications

Neurological complications of COVID-19 were reflected in 14 research studies:

• Guillain–Barré syndrome (0.19%): A rare and serious condition that impacts the nerves
• Encephalitis (0.19%): Inflammation of the brain
• Cerebral hemorrhage (0.5%): Bleeding in the brain
• Glossopharyngeal neuralgia (3.7%): Severe pain in the throat, ear, tongue, and tonsils
• Acute ischemic stroke (4.6%): A loss of blood in an area of the brain
• Impaired consciousness (9.6%)
• Delirium (13.1%): A feeling of confusion
• Muscle pain (15.1%)
• Hyposmia (20.4%): A decreased sense of smell
• Seizures including hypoxia (27%): Seizures that are linked with low levels of oxygen in the body
• Encephalopathy related to fever or hypoxia (35.2%): Brain dysfunction caused by fever or low oxygen levels in the body
• Anosmia (79.6%): Partial or full loss of smell
• Aguesia (83.38%): Loss of the sense of taste
• Gustatory dysfunction (88.8%): An altered sense of taste
• Ischemic stroke (90.9%): A stroke in which blood supply to the brain is blocked or reduced

Again, researchers relied on case reports to learn about potential outcomes of these neurological symptoms. Of the 11 patients observed in 10 case reports, seven patients were cured, and two were still hospitalized and receiving treatment at the end of the study period.

Renal System Complications

The renal system—also known as the urinary system—consists of the kidneys, bladder, ureters, and urethra. Researchers observed renal system complications in 16 studies:

• Hypoproteinemia (6.5%): Low protein levels
• Acidosis (12%): Body fluids are too acidic
• Hyperkalemia (23%): High potassium levels
• Hematuria (26.7%): Blood in the urine
• Alkalosis (28%): Body fluids are too alkaline
• Proteinuria (43.9%): High levels of protein in the urine
• Acute kidney injury (68.8%): When the kidneys suddenly stop working

The data about potential outcomes of these symptoms is reflective of only seven patients across seven case studies. Of those, five were cured or improved, one patient died, and one patient was discharged but wasn’t completely cured.

 Cardiovascular System Complications

Eighteen research studies explored cardiovascular system complications of COVID:

• Arrhythmia (16.7%): Irregular heartbeat
• Venous thromboembolism (25%): Blood clotting in a vein
• Coagulopathy (34.4%): A bleeding disorder
• Acute cardiac injury (44%): A range of conditions related to sudden and reduced blood flow to the heart
• Non-coronary myocardial injury (55.56%): A range of conditions that interfere with the body’s ability to pump blood
• Disseminated intravascular coagulation (71.4%): Abnormal clotting throughout the body’s blood vessels

Based on limited data from 11 case reports of people who experienced these complications, five patients improved or were cured, and two died.

Why These Findings Matter

These findings are valuable for doctors because they help clinicians understand the full scope of what the virus can do to a person, infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Verywell.

What’s not clear from the findings is whether being vaccinated against COVID-19 lowered the odds of developing these rare complications.

"I anticipate that vaccination might prevent these complications from occurring,” William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, told Verywell. “Some of these are quite serious.”

But Adalja said that it’s difficult to know for sure.

“[Vaccine protection] will vary depending upon the actual causes of the symptoms, because many symptoms are the result of the immune response to the virus combined with the direct actions of the virus,” he said.

The researchers urged healthcare practitioners in the study to monitor COVID-19 patients for these complications and not focus exclusively on treating respiratory symptoms.

“Post-COVID effects should be monitored, and follow-up of patients should be performed on a regular basis to check for long-term complications,” the researchers wrote.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.