We sequentially examined the liver sections of the first 44 COVID-19 autopsies at our institution; however, four were excluded for severe autolysis resulting in a cohort of 40 patients. The overall median (IQR) age was 70 (66–80) years and 29 (70%) were men. Twenty-three patients were Hispanic, five were African American, and two were Caucasian (the remaining ten were unknown). Seven of the patients had died on arrival, and had either no or limited clinical data. The median length of stay was 8.5 days. Twenty-two patients (55%) received steroids during their admission, 19 (47.5%) received hydroxychloroquine, and six (15%) received tocilizumab (this cohort was encountered before remdesivir was widely used, and none of these patients received it). Patient characteristics and known comorbidities are summarized in Table 1.
There were two patients with evidence of chronic liver disease, one with alcohol-related cirrhosis and one with a history of liver transplant for autoimmune-related liver disease and acute cellular rejection at the time of admission. Five patients had imaging evidence of NAFLD on admission. In addition, one patient with imaging evidence of steatosis also had an isolated anti-hepatitis B (HBV) core antibody positive with low-level HBV DNA detected.
Initial and peak laboratory values including liver enzymes and inflammatory markers are displayed in Table 2. The median initial and peak AST and ALT were 1–3 times the upper limit of normal, while median TB values were in the normal range. Kidney dysfunction was common with a median peak creatinine of 2.64 mg/dl (upper limit of normal = 0.98 mg/dl for females and 1.30 mg/dl for males). Median peak levels of inflammatory markers including CRP (268 mg/l, upper limit of normal = 10 mg/l), ferritin (1810 ng/ml, upper limit of normal = 150 ng/ml for females, 400 ng/ml for males), D-dimer (9.6 μg/ml, upper limit of normal = 0.8 μg/ml), and IL-6 (>315 pg/ml, upper limit of normal = 5 pg/ml) were all markedly elevated. There were no significant associations between laboratory values and any specific histological feature (data not shown).
Grossly, two livers showed fibrosis and one had abscesses, the remaining livers showed varying degrees of steatosis, congestion, and ischemia, but no other significant gross pathology. Histologically, the most frequently encountered findings were macrovesicular steatosis, mild acute hepatitis, and minimal-to-mild portal inflammation. Various less frequent findings were also observed. The findings are described below and major findings are summarized in Table 3. As the focus of this study is liver pathology, the lungs were considered only in the context of how the pulmonary findings may relate to liver injury. Overall, 29 of 40 patients (73%) had evidence of ALI histologically (the gross appearance of the lungs was not reviewed for this study). The patients with ALI did not differ from those without with respect to any of the laboratory variables we cataloged, or to any histologic findings (data not shown). There was, however, a trend toward increased serum CRP in the ALI group (282 mg/l vs. 218 mg/l, p = 0.07).
Steatosis was common, effecting 30 patients (75%), Fig. 1a. Fat droplets were predominantly macrovesicular and no case of true microvesicular steatosis was encountered. Two cases (7%) had active steatohepatitis with ballooning and Mallory–Denk bodies. Nineteen patients (48%) had mild fat (6–33%), six patients (15%) had moderate fat (34–66%), and five patients (12%) had marked fat (>67%). Most commonly, the fat was panlobular (zones 1, 2, and 3; periportal to centrilobular, 18 cases, 53%). The fat was restricted to the centrilobular region (zone 3) in seven cases (21%), while it was located in zones 2 and 3 in three cases (8.8%). Ten (33%) cases had “mismatched” fat, in which the steatosis was mild, but the fat involved periportal (zone 1) hepatocytes. A BMI was calculable in 32 patients. Two of 32 had a BMI over 35. There was no correlation between BMI and percent steatosis (Spearman’s r = −0.04, p = 0.84). Similarly, there was no association between length of stay and percent steatosis (p = 0.57) or distribution (zonality) of steatosis (p = 0.80). Half of the patients in whom we had data (18 of 36) were diabetic. Having a history of diabetes mellitus was not associated with percent steatosis (p = 0.48) or distribution of steatosis (p = 0.43). Treatment with corticosteroids was not associated with percent steatosis (p = 0.35) or distribution of steatosis (p = 0.87).
A total of 20 cases (50%) showed features of acute hepatitis, defined as the presence of lobular necroinflammation, Fig. 1b. These foci contained lymphocytes and rare histiocytes. Plasma cells were rare. Sixteen of these cases were of mild severity (80%) and four were of moderate severity (20%). No severe hepatitis (e.g., submassive necrosis, massive hepatic necrosis, bridging necrosis) was encountered. Four patients without necroinflammation showed rare, individual apoptotic hepatocytes. Given the focality of the finding (one or two such cells in one or two sections of liver), the significance of this observation is uncertain. Six cases with lobular necroinflammation also demonstrated occasional individual apoptotic hepatocytes, Fig. 1c. Lobular mitoses were seen in three cases (8%). Two of these cases also had acute hepatitis, whereas one occurred in an allograft which did not demonstrate active hepatitis. There were no associations between lobular necroinflammation and length of stay (p = 0.87), hydroxychloroquine treatment (p = 0.73), or tocilizumab administration (p = 0.17).
Twenty patients (50%) had portal inflammation. Three cases had interface hepatitis (equivalent to Batts–Ludwig Grade 2, Fig. 1d), whereas 17 had only minimally increased portal mononuclear cells (lymphocytes and few portal macrophages). One of the cases with interface occurred in an allograft with recent severe rejection with autoimmune features (ACR-AIH). Eosinophils and neutrophils were rare, and not prominent in any case. An occasional plasma cell was present, but in none of the cases were they significant enough to invoke consideration of autoimmune hepatitis or drug induced liver injury with autoimmune features (DILI-AIH), with the exception of the ACR-AIH case. No case demonstrated lymphoid aggregates. Overall, 6 of the 20 patients did not have evidence of lobular/acute hepatitis. Of these one was the ACR-AIH patient and two came into the emergency room in cardiopulmonary arrest, and without history in our system. There were no associations between portal inflammation and length of stay (p = 0.86), hydroxychloroquine treatment (p = 0.20), or tocilizumab administration (p = 0.10).
In cases with acute, severe cardiac dysfunction areas of congestion (right heart failure) and ischemia (left heart failure) are common regardless of etiology. In our series, 32 (78%) patients exhibited congestion and 16 (40%) exhibited centrilobular ischemic necrosis.
Fifteen (38%) cases had lobular cholestasis, generally mild and focal. Four of these 15 cases (10% of series) had ductular cholestasis, indicative of sepsis. Interlobular bile ducts were present in a normal distribution in all cases (no ductopenia) and the ducts were normal appearing (tubular structures composed of cholangiocytes with maintained polarity) in 39 of 40 cases (the ACR-AIH case had duct dysmorphia).
None of the cases had diffuse vascular pathology; however, focal findings were identified. Phlebosclerosis, reminiscent of veno-occlusive disease (VOD) was present in six cases, Fig. 2a. In five cases, this occurred in a portal venule, but one case had involvement of the central vein. Portal arterioles were abnormal in nine cases. Three of these had arteriolar muscular hyperplasia, Fig. 2b. Each case with muscular hypertrophy of the portal arterioles also had venous phlebosclerosis. Four cases had hyalinosis of the vessel wall (Fig. 2b). Two cases had fibrinoid necrosis with endothelial apoptosis (Fig. 2c). Sinusoidal microthrombi were present in six cases (Fig. 2d). C4d immunohistochemistry (IHC) was performed on ten cases and was negative (either entirely or almost entirely negative in all cases).
Three cases had granulomatous inflammation. One case had portal and lobular granulomas reminiscent of “fibrin ring” morphology, Fig. 3a. This patient had been treated with a number of potentially hepatotoxic medications throughout the hospital course including hydroxychloroquine and tocilizumab for severe COVID-19, as well as amiodarone for atrial fibrillation and ceftriaxone and piperacillin/tazobactam for infection. One patient had multiple necrotizing granulomas forming grossly appreciable abscesses and had structures suggestive of Schistosoma eggs. The final case demonstrated portal non-necrotizing granulomas in two portal tracts and resembled primary biliary cholangitis (PBC). However, the patient was male, had no known history of PBC, and had a normal alkaline phosphatase.
Two cases had pale ovoid sinusoidal inclusions, which at low power resembled apoptotic hepatocytes. Upon close examination, it became evident that these inclusions were present in the sinusoidal spaces, Fig. 3b. We stained these with CD61, which was positive (Fig. 3b inset), supporting that these aggregates were rich in platelets. We chose to refer to these structures as “thrombotic bodies.”
PCR was performed on 20 autopsy livers and was positive in 11 (55%) ranging from 10 copies to 9254 copies/μl RNA. The longest interval between initial diagnosis by nasopharyngeal swab and death was 25 days and the median was 13 days. There was no relationship between time from initial diagnosis (positive nasopharyngeal swab) and likelihood of PCR positivity in the liver at autopsy (p = 0.51). We investigated whether PCR positivity was associated with any laboratory parameters (Table 4). Median peak AST was higher among patients with a positive PCR compared to negative (239 vs. 86 U/l, respectively) though this did not reach statistical significance (p = 0.063). In addition, peak ferritin (3623 vs. 1014 ng/ml, p = 0.048) and peak creatinine (4.50 vs. 2.02 mg/dl, p = 0.025) were significantly higher among PCR positive patients. There were no significant correlations between PCR positivity and any histologic finding including congestion (Supplementary Table 1).