Peritoneal carcinomatosis (PC) is the intraperitoneal dissemination of any tumour that does not originate from the peritoneum itself. It is the most common diffuse peritoneal disease. Improvement in its diagnosis and treatment affects its prognosis .
The present prospective study included 30 patients with malignant tumours suspected to have peritoneal carcinomatosis. The study patients included 22 females (73.3%) and eight males (26.7%) with ages ranged from 39 to 85 years and a mean age of 61.5 ± 11.1 years. In the present study, PETCT was able to diagnose 16 out of 30 patients with sensitivity (76.2%) and specificity (88.9%). The examination showed a positive predictive value (PPV) (94.1%), negative predictive value (NPV) (61.5%) and accuracy (80.0%).
Out of 17 patients included in this study and diagnosed with peritoneal carcinomatosis using PET/CT, 16 patients were true-positive on follow-up. Only one false-positive patient was found after follow-up and negative histopathological examination.
Out of 13 patients included in the present work and excluded to have peritoneal carcinomatosis by PET/CT, on follow-up, eight patients were true-negative and five patients were false-negative.
Soussan et al.  were consistent with our findings. The study reported good sensitivity (84%) and specificity (84%) as well as accuracy (80%) for PET/CT in the diagnosis of peritoneal carcinomatosis.
In this study, the range of SUVmax of FDG uptake among all enrolled patients was 1.3–25.0, and the mean SUVmax of FDG uptake was 8.04 ± 6.14. The best cut-off value of SUVmax was 5 for the diagnosis of peritoneal carcinomatosis with statistical significance (p = 0.001).
Suzuki et al.  also reported that the use of an intra-abdominal FDG uptake cut-off value for SUVmax of > 5.1 assists in the diagnosis of peritoneal carcinomatosis, which is in line with our findings.
In the current study, different patterns of FDG uptake of peritoneal carcinomatosis were found as follows: focal nodular uptake, diffuse abdominal uptake and liver surface focal or diffuse uptake. Moreover, focal nodular uptake was the most frequent pattern seen in 25 patients (51%).
Funicelli et al.  found that the [18F] FDG-PET/CT examination showed 47 nodular uptakes (75%) of the 62 nodules reported at surgery; the diffuse uptake pattern was seen in seven scans (70%) of the ten reported at the surgery.
Different primary tumours were included during the study. Colonic mucinous adenocarcinoma, poorly differentiated gastric adenocarcinoma, ovarian serous cystadenocarcinoma and MUP were the most frequent primary tumours to disseminate to the peritoneum.
Agreement with other studies like Campos et al.  reported that the ovary, colon and stomach are the most frequent sites of origin for secondary peritoneal neoplasms.
Among the studied patients, the greater omentum was the most frequent site of peritoneal metastasis from most of the tumours included.
Patel et al.  reported that peritoneal metastases are common within the greater omentum. Moreover, a normal-appearing omentum either on imaging or surgical macroscopic inspection is found to have microscopic peritoneal metastases on histology.
Our study had some limitations. Histological assessment was not performed for all patients. The major drawbacks of PET imaging are its radiation exposure, higher cost and limited depiction of small tumour volumes (current spatial resolution 4 mm) because most of the peritoneal tumour implants are small nodules. Other limitations include the underestimation of uptake due to physiologic movements of the bowel and the normal uptake by the liver, stomach and colon which is sometimes difficult to distinguish from that of peritoneal carcinomatosis.