a lip switch flap is an axial - pattern flap using the inferior labial artery as a feeding blood vessel . its morphology is appropriate to improve the upper lip morphology in the presence of severe cleft lip and nose deformity . it is capable of simultaneously reconstructing the philtrum and extending the bridge of the nose , and was reported to be very useful and be associated with fewer complications in many cases.[14 ] cutting et  al . described it was very important to proceed in secondary bilateral cleft lip reconstruction with lip switch flap only after the midface and nose repair done . on the other hand , the vascular pedicle of this flap is very thin and circulatory disorder occurs due to 180 rotation of the pedicle , being a risk for flap necrosis . the grafted flap was returned to the donor site to improve blood circulation of the flap , followed by its re - transplantation , which prevented necrosis of the flap . here , severe cleft lip nose deformity , i.e. a short bridge and flat apex of the nose , were observed . under general anesthesia , the nasal morphology was improved using cartilage of the nasal septum , and the lip deformity was improved by forming a tubercle of the upper lip using a lip switch flap with left inferior labial arterial and venous pedicles , the philtrum and bridge of the nose . the lower lip flap was designed to have a 10-mm width and a 17-mm length and transplanted to the upper lip . its color immediately after surgery was favorable ( figure 1(a ) ) , but marked swelling of the flap and surrounding tissue was noted 6  h after surgery , with which the flap developed venous congestion ( figure 1(b ) ) . to release pressure due to the swelling on the vascular pedicle , sutures around the pedicle were removed , but blood circulation of the flap did not improve and congestion aggravated . since flap necrosis was predicted , the flap that had been transplanted to the upper lip was returned to the lower lip 8  h after surgery to improve its blood circulation and prevent necrosis . under venous sedation , the flap transplanted to the upper lip was released to a free state so that the mouth could be opened , oropharyngeal intubation was applied and sedation was switched to general anesthesia . hematoma around the flap was removed by washing well with saline . after confirming blood flow from the flap stump , the flap was returned to the lower lip and fixed by sutures , and the transplantation site was simply sutured ( figure 1(c ) ) . ( a ) at the completion of surgery , ( b ) 6  h after surgery and ( c ) the flap was returned to the lower lip . after surgery , the flap was covered with heparinized saline - soaked gauze to further reduce congestion . congestion was improved 7  h after surgery ( figure 2(a ) ) , and the flap returned to the donor site had almost completely recovered 1 week after surgery ( figure 2(b ) ) . the flap was re - transplanted with sufficient tissue around the pedicle under local anesthesia ( figure 2(c ) ) . as of 2 years after surgery ( figure 2(d ) ) , the cleft lip nose deformity had improved with a favorable course . ( a ) seven hours after returning the flap to the donor site , ( b ) 1 week after surgery , ( c ) re - transplantation of the lip switch flap and ( d ) 1 week after surgery . in cleft lip patients with upper lip tissue defects , a complication of a lip switch flap , flap necrosis , results in failure of upper lip reconstruction . the feeding artery of a lip switch flap , the inferior labial artery , is distributed within 15  mm from the upper end of the lower lip . it is very thin , and 180 rotation of the vascular pedicle is likely to cause ischemia due to twisting and pressure . since the vein distributing along with the inferior labial artery is unclear , venous perfusion by the surrounding oral mucosa but , when oral mucosa is too thick , there is the problem that the shape of upper lip comes to worse . similarly , when pressure is loaded on the vascular pedicle and surrounding tissue by tension induced by flap rotation and swelling after surgery , venous congestion readily occurs , being a risk for partial or total necrosis . since the vascular pedicle of the flap is very thin , the risk should be fully considered , and we encountered it in 2 of 32 patients treated over the last 10 years . in the present patients , venous congestion was treated by removing sutures around the vascular pedicle to release tension loaded by the surrounding tissue , such as mucosa and muscle , and phlebotomy was also applied , but these were ineffective , and congestion of the flap rapidly progressed , being likely to result in total necrosis . we considered the application of medical leeches to improve congestion , but this was abandoned because the patient rejected it and the progression of congestion was rapid due to the small size of the flap . when severe venous congestion develops in a lip switch flap , like this case , it is likely to rapidly progress and result in total necrosis . thus , the early discovery of congestion by careful observation of the flap after surgery and rapid treatment upon suspecting congestion are very important . the flap could be re - transplanted after it was returned to the donor site to sufficiently recover circulation in tissue around the vascular pedicle , and it engrafted and achieved a favorable upper lip morphology , reconfirming that , when congestion is suspected , the flap should be treated without hesitation . various modifications have recently been added to the previous lip switch flap , and the vascular pedicle was further thinned to improve mobility in some modifications . in these two cases , attention should be paid to venous congestion , and preparation for its treatment may be important . the authors report no conflicts of interest . the authors alone are responsible for the content and writing of this article .