the invention described below is an example of implementation of the novel orogastric catheter according to the invention , referring to the appended drawings in which : fig1 to 3 show , respectively , the anatomy of the stomach and two elements of the prior art ; fig4 is a general view of the novel orogastric catheter formed by a tubular body of circular section in silicone , the distal end of which is equipped with an inflated balloon , intended to become lodged in the pyloric antrum ; fig5 is a detail side view of the distal part of the catheter on which the inflated balloon is mounted ; fig7 is a side view of the distal part of the catheter with the balloon in the deflated state ; fig8 is an enlargement of fig7 according to a perspective view from ¾ front ; fig9 is a schematic diagram showing the placement of the catheter in the stomach . the orogastric catheter shown in its entirety in fig4 and denoted by the general reference 20 comprises a tubular body 21 of silicone , of right circular cross - section . this tubular body 21 has an open proximal end 22 and a distal end 23 , equipped with a distal tip 24 . the outside diameter de shown in fig5 to 8 of this tubular body 21 is for example 12 . 5 mm , or 37 . 5 fr ( french bougies ). this outside diameter de calibrates the volume of the stomach - 1 - to be preserved . thus , several diameters of this tubular body 21 and therefore several calibres can be offered to the surgeon . the total length of the tubular body 21 from the proximal end 22 to the distal end 23 is , for example , 900 mm . the tubular body 21 advantageously has a sufficient total length so that its distal part , in particular the inflated balloon 25 , can be placed in the pyloric antrum - 4 - of the stomach - 1 - ( cf . fig1 and 9 ). the tubular body 21 is preferably made of transparent silicone elastomer . its structure , and its mechanical properties , in particular including its elasticity , are selected in such a way that the rigidity of the catheter is sufficient so that it can be introduced via the patient &# 39 ; s mouth as far as the stomach , passing through the oesophagus , without damaging the walls of the alimentary canal , while preserving a substantially rectilinear shape to match the anatomical morphology of the patient &# 39 ; s stomach - 1 -, in particular of the lesser curvature - 6 - of the stomach in the case of the tubular body 21 and the pyloric antrum - 4 - in the case of the inflated balloon 25 . thus , the tube e . g . of silicone elastomer forming the body of the catheter , the latter advantageously has a shore hardness of 65 ± 10 . advantageously , the tubular body 21 of the catheter 20 is graduated from 5 cm in 5 cm steps ( 10 graduations ) starting from the distal end 23 . moreover , the distal part of tube 21 of the catheter 20 carries a balloon 25 that has , in the inflated state , a shape substantially matching that of the pyloric antrum - 4 -. this balloon 25 is mounted on the outer face ( right anatomical face — fig9 -) of the wall of the tubular body 21 , in such a way that the median longitudinal plane of the inflated balloon 25 corresponds approximately to the median longitudinal plane of the tubular body 21 . these median longitudinal planes of the inflated balloon 25 and of the tube 21 are roughly equivalent to the frontal plane of anatomical section ( fig9 ). this inflated balloon 25 has a general asymmetric and distorted truncated cone shape with , on the one hand , a terminal diameter dt , a diameter at the base db , and a diameter dm of the middle part such that dt & lt ; db ≦ dm , and , on the other hand , an end 26 that is offset , relative to the axis 27 of the base of the inflated balloon 25 , upwards , towards the part of the tubular body 21 of the catheter 20 arranged above the inflated balloon 25 , in such a way that the upper face of the inflated balloon 25 intended to be arranged opposite the angular notch - 9 - of the stomach - 1 -, has an upper curvature 29 { between points cst and csb in fig5 } of the upper face 28 , less pronounced than the lower curvature 30 { between points cit and cib in fig5 } of the lower face . the radius of curvature of the upper curvature 29 ( cst - csb ) is greater than that of the lower curvature 30 ( cit - cib ). the height h of the inflated balloon 25 is measured in the median longitudinal plane of the tubular body 21 and of the inflated balloon 25 , from the edge of the tubular body 21 located just upstream of the distal tip 24 and downstream of the balloon 25 ( right side of the stomach ), to the top of the inflated balloon 25 ( see fig5 ). in other words , the dimensions and the elasticity of the balloon 25 are such that the volume of the inflated balloon can for example be 75 cm 3 +/− 25 cm 3 . according to another feature of the invention , the upper face 28 of the inflated balloon 25 intended to be arranged opposite the angular notch - 9 - ( cf . fig1 and 9 ) of the stomach - 1 - makes , with the tubular body 21 of the catheter 20 , an angle a equal , in this example , to about 90 ° ( cf . fig5 ). as is clear from fig5 , the angle a is defined by the straight line passing through the two points csb and cst of the inflated balloon ( 25 ) and by the tubular body 21 - generator g . this balloon 25 consists of a membrane , for example of silicone elastomer preferably made from several superposed annular segments 31 , integral with one another , and with dimensions selected to give the inflated balloon 25 the shape described above and shown in fig4 , 5 , 6 and 9 . the base of balloon 25 has a lip 32 welded and / or glued on tube 21 of the catheter 20 . as can be seen in fig7 and 8 , the base 32 of balloon 25 envelops tube 21 on a large part of its circumference . moreover , as shown in fig7 , the distance d between , on the one hand , the distal end of tube 21 corresponding to the distal end 23 of tip 24 and , on the other hand , the point of the base of the inflated balloon 25 closest to this distal end 23 , is , for example in the present case , 10 mm . it is advantageous that d should be as small as possible , so as to adapt best to the anatomical shape of the pyloric antrum - 4 -. this rounded distal tip 24 is pierced in its centre with a hole 33 so that the lumen of tube 21 communicates with the exterior , in the same manner as the oblong lateral holes 34 present in the distal part of the tube 21 , upstream of the balloon 25 . these orifices 33 , 34 permit the withdrawal and injection of gaseous or liquid fluids of the stomach . according to the invention , calibration of the part of the stomach to be preserved is not only provided by the outside diameter de of the tubular body 21 , but also by the volume of the inflated balloon 25 . several volumes of inflation of the balloon 25 give as many calibres to the surgeon . the catheter 20 is also provided with a positioning reference mark 36 . this reference mark 36 is formed by a contrasting mark on the entire length of the wall of tube 21 from the proximal end 22 to the distal end 23 . it is perpendicular to the axis 27 of the inflated balloon 25 , in the median longitudinal plane common to said inflated balloon 25 and to the tube 21 . it is placed on the right side of the stomach , i . e . the side where the balloon 25 can be inflated in the pyloric antrum - 4 -. in particular it indicates to the surgeon the outer face of the wall of tube 21 on which the balloon 25 is mounted ( anatomical right side in fig9 ). this face is then in abutment against the lesser curvature . placement of the inflated balloon 25 in the pyloric antrum - 4 - is thus greatly facilitated by this contrasting reference mark 36 . the catheter 20 according to the invention is also equipped with a tube 37 connecting the balloon 25 to the proximal end 22 of the tubular body 21 and allowing inflation / deflation of said balloon 25 from this proximal end , by means of an inflating means , which can be for example a bulb 38 provided at the proximal end 37 connected to the exterior via a valve 39 , and / or a fluid ( e . g . air ) injector such as a syringe , which can be introduced into the tip of tube 37 upstream of valve 39 . the inflating tube 37 of the balloon 25 passes along within the thickness of the wall of the tubular body 21 on the same side as the positioning reference mark 36 or on the other side . the distal end of the inflating tube 37 opens inside the distal balloon 25 . fig9 shows the stable position of the distal part of the tubular body 21 against the lesser curvature - 6 - and the wedging of the inflated bulb 25 in the pyloric antrum - 4 -. the positioning of the inflated balloon 25 and of the distal part of the tubular body 21 shown in fig9 provides the surgeon with anatomical reference points and a guide for carrying out resection - stapling of the left part of the stomach - 1 - to be removed ( dot - and - dash line in fig9 ), following the calibration also defined by the inflated balloon and the distal part of tube 21 in abutment against the lesser curvature - 6 -. the optional deflecting means that can allow folding of the distal part of the catheter , for example 88 mm from the distal end , by an angle e . g . of about 90 °, comprise a cable or pull - cord system inserted in a channel coaxial with tube 21 on the right side of the stomach , where the balloon 25 is located . the cable passes down through this canal and is fixed in the distal part of the catheter . above the fixing point of the cable , and of the distal tip 24 of the catheter 20 , a notch with an angle of about 45 ° is made in the body 21 of the catheter 20 so as to create a folding line . a membrane is glued on the notch to ensure hermeticity of the body of the catheter . once the catheter is in place in the patient &# 39 ; s stomach - 1 -, the cable can be tightened by the action of the surgeon &# 39 ; s hand at the proximal part of the catheter , and this action leads to folding or deflection of the terminal distal part of the tubular body 21 which forms an angle , for example of 90 °, with the upper part of said tubular body 21 . the lumen of the tubular body 21 can allow introduction of visualizing means such as a light source , for example a flexible optical fibre . it is possible to envisage a surface treatment of the outer face of the tubular body 21 and of the balloon 25 , so as to reduce the coefficient of friction and thus facilitate sliding of the catheter 20 against the internal tissues of the patient &# 39 ; s alimentary canal . as shown in fig9 , this orogastric catheter 20 can be introduced , prior to longitudinal gastrectomy , in the patient &# 39 ; s mouth until its distal end 23 reaches the stomach - 1 -. the sequence of longitudinal gastrectomy then consists of exsufflation of the stomach in the case of air distension induced by the intubation manoeuvres during anaesthesia , then inflating the balloon 25 and lodging it in the pyloric antrum - 4 -, in such a way that : the end 26 of the inflated balloon 25 is for example in abutment against the pylorus - 5 - ( shown by dotted lines in fig9 ), so that the distal end 23 of the tubular body 21 is for example in abutment against the pyloric antrum - 4 -, for example about 5 to 10 cm from the pylorus - 5 -, and so that the part of the tubular body 21 of the catheter 20 arranged above the inflated balloon 25 is wedged against the wall of the lesser curvature of the stomach 6 . the surgeon can then proceed , using a suitable tool , to resection - stapling of the left part of the stomach ( dot - and - dash line in fig9 ), guided by the inflated balloon 25 and the distal part of tube 21 , which itself indicates the start of the closure resection line and said closure resection line itself , also supplying , in addition to these anatomical reference points , a support for his closure resection instrument . the inflated balloon 25 and the distal part of tube 21 also calibrate the gastric sleeve and the pyloric antrum 4 to be preserved . after resection of the left part and stapling , it is possible to inject coloured liquid in the patient &# 39 ; s stomach 1 for verifying the hermeticity of the closure line . the light source for visualizing the interior of the stomach can be introduced in the tubular body 21 at any time during the procedure . the surgeon is thus provided with a multifunction orogastric catheter that enables him to perform high - quality longitudinal gastrectomy rapidly and in complete safety for the patient .