Intraperitoneal pressure and intra-abdominal pressure: are they the same?

In peritoneal dialysis (PD), a standard therapy for patients with end-stage renal disease (ESRD), the effects of using the peritoneum as an exchange membrane and of dialysate dwelling within the peritoneal cavity creates some mechanical changes, including an increase in intraperitoneal pressure (IPP) that might lead to intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). The diagnosis of IAH and ACS depend on intra-abdominal measurement of IAP by an indirect technique. There is no clear distinction between IPP and intra-abdominal pressure (IAP). Our objective in this study was to find if there is real difference between IPP and IAP.

This study was conducted at the PD unit of King Fahd Hospital of the University, Al-Khobar, between July 2008 and January 2009. To be included, patients had to have known ESRD for at least 5 years, to be 18 years of age or older at enrollment, with stable body weight and blood pressure, and with no clinical signs of overhydration. Patients with congestive heart failure III and IV (New York Heart Association criteria) and severe pulmonary disease, psychiatric illnesses, neurogenic bladder, known history of peritonitis, or medical or surgical abdominal intervention in the preceding 3 months were excluded. We measured IAP by the direct technique through the peritoneal catheter and by an indirect technique using an intravesical catheter.

The 25 patients who met the inclusion criteria included 13 men and 12 women, with a mean age of 53 ± 2 years (range: 18 - 76 years). The predominant causes of ESRD were diabetes mellitus and glomerulonephritis. Mean IPP in the dry state (supine) was 9.49 ± 5 mmHg, and mean IAP was 9.4 ± 5.4 mmHg (p = 0.9). In the dry state (erect), the mean IPP increased to 16.9 ± 7.2 mmHg, and the mean IAP, to 16.4 ± 6.9 mmHg (p = 0.8). In the filled state (supine), mean IPP was 12.6 ± 4.7 mmHg, and mean IAP, 12.8 ± 4.8 mmHg (p = 0.88); the erect pressures were 21.4 ± 7 mmHg and 21.6 ± 6.9 mmHg respectively (p = 0.9).

Our findings indicate that there is no statistical difference between IPP and IAP in either the erect or the supine position.