Because current standard guidelines do not recommend abdominal computed tomography (CT) for the initial evaluation of patients with Ph^- MPN, abdominal CT is not routinely performed at the time of MPN diagnosis [4], and is only performed in patients with relevant symptoms or signs [5]. However, abdominal CT scans performed at the time of diagnosis of Ph^- MPN may provide useful clinical information. For instance, splanchnic thrombosis is often asymptomatic and may be detected in MPN patients at the time of diagnosis [6]. As previously reported, abdominal CT detects volumetric splenomegaly in all pre-PMF patients and in only 50% of ET patients at diagnosis [7]. PV patients with volumetric splenomegaly at diagnosis had a poorer prognosis than those without; however, the prognosis is better than that of patients with palpable splenomegaly [8]. In addition, abdominal CT performed at the time of MPN diagnosis revealed asymptomatic splenic infarction [9] and abdominal aortic calcification, indicative of a poor prognosis (submitted for publication). Several cancers are more common in Ph^- MPN patients than in the general population [2, 10]. The cumulative incidence of malignancies tends to increase immediately after MPN diagnosis [2], suggesting the possibility of pre-existing malignancies at diagnosis. Because malignancies are more common in the abdominal and pelvic cavities, abdominal CT performed at the time of MPN diagnosis may detect such malignancies. Besides the information on the spleen or abdominal aortic calcification that has already been reported in Ph^- MPN patients, this study retrospectively analyzed the incidental findings of abdominal CT scans performed at the time of MPN diagnosis.

Patients who were diagnosed with ET, PV, pre-PMF, or PMF and who had undergone abdominal CT at the time of diagnosis (between January 2002 and December 2021) at Chungnam National University Hospital, Daejeon, Korea, were enrolled. The medical records of the enrolled patients were reviewed. We did not record the presence of volumetric splenomegaly, splenic infarction, abdominal aortic calcification, or prostate abnormalities. Before 2016, abdominal CT was performed in selected patients with relevant symptoms or signs to identify splenomegaly and confirm the diagnosis. Subsequently, abdominal CT was routinely performed for the initial evaluation of patients at the time of MPN diagnosis. For patients diagnosed with ET before 2017, the diagnosis was revised on the basis of the 2016 World Health Organization diagnostic criteria [11]. During the study period, 365 patients (150 with ET, 48 with pre-PMF, 136 with PV, and 31 with PMF) were newly diagnosed with Ph^- MPN. Of these patients, we enrolled 219 (60.0%), including 94 with ET (median age, 62 yr; range, 18–90 yr), 24 with pre-PMF (median age, 67.5 yr; range, 31–88 yr), 80 with PV (median age, 64.5 yr; range, 18–66 yr), and 21 with PMF (median age, 64.5 yr; range, 18–90 yr). The patients were followed-up for a median of 3.4 years (range, 0.1–20.2 yr).

The most frequent findings were renal cysts (N=67, 30.6%), followed by hepatic cysts (N=38, 17.4%), gallstones (N=26, 11.9%), fatty liver (N=12, 5.5%), hepatic hemangioma (N=10, 4.6%), and duodenal diverticulum (N=9, 4.1%). The proportion of patients with these findings did not differ according to the MPN subtype. Hepatic calcification was more frequent in PMF patients (4 of 21; 19.0%) than in those with other MPN subtypes (P<0.001) (Table 1). However, its clinical implications remain unclear. Owing to the non-inclusion of healthy individuals as controls, we could not ascertain whether these findings are more prevalent in Ph^- MPN patients than in the general population. However, these lesions are frequently detected in the general population, and their prevalence does not appear to differ from that in our study patients [12-15]. Logistic regression analysis was performed to identify risk factors for incidental findings. Older age (>60 yr) was the only independent risk factor for renal cysts (Table 2). No independent risk factors were detected for the other findings (data not shown). Incidental CT findings did not affect the likelihood of thrombosis or overall survival (data not shown). Therefore, these lesions appeared to be incidental.

Of the 219 Ph^- MPN patients enrolled, 3 (1.4%) had splanchnic thrombosis, and 2 developed splanchnic vein thrombosis. Abdominal CT was performed in one PV patient because of abdominal distension and pain, which revealed thrombosis of the portal, splenic, and superior mesenteric vein, with marked splenomegaly. Another ET patient developed asymptomatic portal vein thrombosis that was detected on an abdominal CT performed during the initial evaluation. One patient with ET developed an asymptomatic left internal iliac artery thrombosis (Table 1). Of the three patients with splanchnic thrombosis, two were asymptomatic, often leading to a missed diagnosis. If abdominal CT had not been performed at the time of diagnosis, this might have led to erroneous risk stratification and treatment.

Of the 219 Ph^- MPN patients enrolled, 4 (1.8%) had an adrenal adenoma and 1 (0.5%) had a benign renal tumor (angiolipoma). Of the 103 female patients, benign ovarian tumors and uterine myomas were reported in 4 (3.9%) and 5 (4.9%) patients, respectively. Malignant tumors were reported in three patients (1.4%); one patient each with ET and PV had renal cell carcinoma. A case of colon cancer has been reported in a patient with ET. None of the patients were symptomatic (Table 1). All patients had early-stage malignancies and had undergone successful surgical treatment. Such malignancies may not be detected at an early stage if abdominal CT was not performed at the time of diagnosis, which may lead to delayed treatment and a poor prognosis.

Our study had some limitations. First, because of the retrospective study design, we could not enroll all patients who presented to our hospital during the study period. Therefore, the prevalence of incidental findings calculated for the study patients may not be representative of all patients with MPNs. Second, because MPNs are relatively rare hematological disorders, the sample size was relatively smaller. Despite these limitations, we found that a small population of Ph^- MPN patients had asymptomatic splanchnic thrombosis and malignant tumors at the time of MPN diagnosis. As mentioned earlier, we previously reported that volumetric splenomegaly and asymptomatic splenic infarction detected by abdominal CT performed at the time of diagnosis are clinically useful for determining the diagnosis and prognosis [7-9]. The advantages of performing abdominal CT may offset the risks associated with radiation exposure and medical costs. Altogether, these data show that performing abdominal CT during the initial evaluation of newly diagnosed Ph^- MPN patients is reasonable.